Hello dear, The lump formation after fall is due to accumulation of fluid & blood and 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 analgesics, ice compression & adequate rest. If it still persists or there are any other associated symptoms like fever, vomiting, excessive crying, loss of consciousness, convulsions, etc...then it will be better to consult her Pediatrician. Under such circumstances, a CT scan of brain will be needed to rule out any pathological cause for symptoms. Wishing her a good health. Take care.