Hello dear... The lump over the forehead after a fall is due to accumulation of blood & it is called hematoma. The blood cells accumulated are eventually broken down and absorbed in the body. But this is a slow process & takes times to disappear completely. Till that time, symptomatic relief is obtained by taking analgesics, ice compression & adequate rest. If it still persists or there are any other associated symptoms like vomiting, loss of consciousness, convulsions, etc...then it will be better to consult your Doctor. Wishing you a good health. Thanks & take care.