What is a bump that won't go away after injury? Common Causes Explained

September 30, 2025 •

5 min read

While most bruises fade within a couple of weeks, a persistent lump after an injury can signal a more complex issue beneath the skin. So, what is a bump that won't go away after injury?, and when should you be concerned? Understanding the potential causes, from leftover blood clots to scar tissue, is crucial for determining if and when to seek medical attention.

Quick Summary

A persistent bump after an injury can be caused by conditions like a long-lasting hematoma, scar tissue (keloid), or fat necrosis. While often benign, the lump's characteristics and symptoms help determine if professional medical evaluation is needed.

Key Points

Differentiate hematoma and bruises: Unlike flat bruises, hematomas are raised, firm lumps of pooled blood that can take much longer to resolve or may require drainage.
Understand scar tissue causes: A keloid is an overgrowth of scar tissue that can continue to expand beyond the initial injury site, requiring medical treatment for removal.
Recognize fat necrosis: Injury to fat tissue can cause cells to die, forming a firm or oily lump called fat necrosis that can persist for a long time.
Monitor for red flags: Seek prompt medical attention for any lump that grows quickly, becomes increasingly painful, is hard and fixed in place, or is accompanied by fever.
Know when to worry about myositis ossificans: A hard, painful mass that develops weeks after a muscle injury and restricts movement could be myositis ossificans, requiring evaluation.
Consider other possibilities: A persistent bump could also be a harmless dermatofibroma, an epidermoid cyst, or in rare cases, a post-traumatic lipoma or cyst.

What is a Persistent Bump After an Injury?

An injury, such as blunt force trauma, can damage the blood vessels and tissues beneath the skin's surface. While the body is typically efficient at repairing itself, sometimes the healing process leaves behind a lingering lump. This can be a simple, benign collection of blood or a more complex issue that requires a doctor's attention. Recognizing the signs of different types of persistent bumps is the first step toward proper care.

Common Causes of Persistent Post-Injury Bumps

Several conditions can result in a bump that lingers long after the initial trauma has occurred. These conditions vary in severity and treatment needs.

Hematoma

A hematoma is a collection of blood that pools and clots in a localized area under the skin following an injury. Unlike a standard bruise, which is flatter, a hematoma forms a noticeable, raised lump.

How it persists: While many hematomas are reabsorbed by the body over time, larger ones can take months to resolve. If the pooled blood hardens or calcifies, it can leave behind a firm, long-lasting mass.
What to look for: A firm, sometimes painful lump that is often discolored (red, purple, black, or yellowish).

Fat Necrosis

Fat necrosis is the death of fat tissue caused by injury and a loss of blood supply. The dying fat cells release their contents, forming a lump that can feel either soft and oily (an oil cyst) or firm and nodular.

How it persists: The body eventually repairs the tissue, but the process can be slow. It's not uncommon for fat necrosis to appear months or years after the initial injury.
What to look for: A painless or slightly tender fatty lump that can be located anywhere with adipose tissue, commonly in the breast or areas of blunt trauma.

Keloid Scar

Keloids are raised, thickened scars that grow well beyond the boundaries of the original wound. This happens when the body's healing process overproduces collagen in response to skin trauma.

How it persists: A keloid can continue to grow for weeks, months, or even years after the initial injury has healed. It will not resolve on its own.
What to look for: A smooth, hard, reddish or flesh-colored bump that is larger than the original injury. They are more common in people with darker skin tones.

Dermatofibroma

A dermatofibroma is a small, firm, reddish-brown bump that typically appears on the legs but can occur anywhere. Its cause is not entirely clear, but they can sometimes form after a minor injury like a bug bite.

How it persists: Dermatofibromas are harmless but won't go away on their own. They can be surgically removed if they are bothersome.
What to look for: A small, firm bump that may dimple inward when pinched.

Lipoma

While not always directly linked to injury, there is evidence that some lipomas, or benign fatty tumors, can be triggered by trauma. This is known as a post-traumatic lipoma.

How it persists: Lipomas grow slowly and can remain for long periods. They are generally harmless and don't require removal unless they are painful or growing rapidly.
What to look for: A soft, doughy, or rubbery lump just under the skin that is easily moveable.

Myositis Ossificans

Myositis ossificans is a less common complication where bone tissue forms inside a muscle or other soft tissue after a severe contusion or hematoma. It most often occurs in the quadriceps and can result in a hard, painful lump.

How it persists: The ossification forms within the muscle, creating a permanent or long-lasting hard mass.
What to look for: A hard, painful mass that develops weeks after a muscle injury and can limit the range of motion.

Comparing Common Persistent Bumps After Injury


Feature	Hematoma	Fat Necrosis	Keloid	Lipoma
Cause	Pooled blood from broken vessels	Death of fat tissue due to trauma	Overgrowth of scar tissue	Benign fatty tissue growth; sometimes post-trauma
Appearance	Raised, discolored lump; color changes over time	Hard or oily lump; may appear dimpled	Thick, raised, and reddish or flesh-colored scar	Soft, doughy, and movable lump under skin
Texture	Firm and tender initially, can harden over time	Can be hard (calcified) or soft (oil cyst)	Firm and rubbery	Soft, rubbery, and easy to move
Healing Time	Varies, can take weeks to months or persist indefinitely	Can resolve on its own, but may take a long time	Does not go away on its own, can continue to grow	Persistent; grows slowly but harmlessly
Treatment	Observation, drainage if large	Generally resolves on its own; can be monitored	Steroid shots, surgery, or laser therapy	Observation, steroid shots, surgery, or liposuction

When to See a Doctor

It is important to monitor any bump that appears after an injury. While many are benign, certain signs and symptoms warrant a professional medical evaluation. You should see a doctor if you observe any of the following:

Rapid growth: If the lump is growing quickly, it's a red flag that should be evaluated immediately.
Increasing pain or swelling: While some discomfort is normal, increasing pain, swelling, or numbness could signal a more serious issue.
Hardness and immobility: A hard lump that is fixed in place and does not move under the skin could suggest a more serious condition.
Systemic symptoms: Accompanying symptoms like fever, night sweats, or unexplained weight loss are red flags for a more serious underlying problem.
Change in appearance: If the lump changes shape, size, or color, or if the skin over it puckers or develops an orange-peel texture, see a doctor.
Not healing: Any bump that does not show signs of improvement after several weeks of conservative management should be examined.

Conclusion

While the sight of a persistent bump after an injury can be worrying, it is most often caused by a common and harmless condition like a healing hematoma or fat necrosis. However, it is crucial to remain vigilant for warning signs such as rapid growth, increasing pain, or immobility. For a bump that won't go away after an injury, the best course of action is to monitor it closely and consult a healthcare provider for an accurate diagnosis and treatment plan, especially if it raises concern. The right response to these lingering issues can ensure a full recovery and prevent unnecessary stress.

For more information on hematomas and other soft tissue injuries, visit the Cleveland Clinic website.

Frequently Asked Questions

A regular bruise involves localized bleeding from smaller blood vessels and is typically flatter. A bump from a hematoma is a larger, raised, and often firmer lump caused by a more significant collection of blood from larger blood vessel leakage.

Healing time varies depending on the size and location of the hematoma. While some small ones resolve in a few weeks, larger hematomas can take several months or even longer for the body to fully reabsorb the pooled blood.

Yes, if an injury causes skin trauma, the body's natural healing process can sometimes lead to an overgrowth of scar tissue, forming a keloid. This is more common in individuals with darker skin tones.

Treatment depends on the cause. Small, benign lumps may only require observation. Others might be treated with aspiration (draining the fluid), steroid injections, or surgical removal. A doctor's diagnosis is necessary to determine the best course of action.

Not necessarily. A soft, rubbery, and easily movable lump under the skin is characteristic of a lipoma, which is almost always benign. However, any new or growing lump should be evaluated by a doctor to ensure a proper diagnosis.

You should see a doctor if the bump grows rapidly, becomes increasingly painful, feels hard and fixed in place, or is accompanied by systemic symptoms like fever or unexplained weight loss. Also, consult a professional if the bump doesn't improve after several weeks.

While fat necrosis is a benign condition and usually harmless, the lumps it creates can sometimes be mistaken for tumors. It's best to have a doctor confirm the diagnosis, especially in areas like the breast, to rule out more serious conditions.