Hello. Thanks for asking from HCM. I can understand your concern. It is good that the mode of injury is not dangerous. Usually hit from door handle is of low force and small momentum. But to avoid any kind of risks, you can observe him for development of signs of dangerous head injury : vomiting : seizures of fits : loss of consciousness : decreasing consciousness : bleeding from nose/ear/throat : onset of new focal deficit like weakness in hand : persistent headache not relieved by medications. If he develops any of above signs, consult ER as soon as possible. The doctor might advise him CT scan of head to rule out fracture or bleed in brain. Further management will be decided after Ct report. Meanwhile, at home you can follow few tips to give him relief : Keep head at higher level than chest. It relieves swelling : Apply icepacks at injury site. Relives swelling and pain. : You can give him pain killer like Diclofenac sodium after proper prescription. It relieves swelling and pain. It does not cause sedation. : In case of vomiting, turn head to side. If still no relief in pain, consult doctor. The swelling will subside in 10-14 days on its own. Hope it will help you. Take care. Thanks.