to your head may therefore result in bleeding under the skin. I f the bleeding is confined to a particular area, a bump or swelling may occur. Such a lump or knot on the ferehead is known as a Hematoma
A swollen lump on the forehead is often caused by an injury or trauma to the head.
If a Sebaceous cyst
causes your bump, the lump would be firm but mobile . Unless there is a infection or inflammation , this type of bump is rarely painful.
Consult with your Doctor.