3 weeks ago i fell and hit my forehead, i had a goose egg immediately with a small cut. i still have a quarter size tender lump, should i be concerned?

No: It is normal and can take quite awhile to resolve completely

Closed head injury: Most serious closed head injuries are associated with loss of consciousness, vomiting, confusion or other neurological signs occurring immediately or shortly after the injury. Rarely, head injuries result in a subdural hematomas, which can produce serious symptoms up to two weeks later. Residual lumps to the skull, lasting for weeks are not uncommon and generally not cause for concern.

Closed head injury: without loss of consciousness , no ataxia , no mental status changes nor gross/ fine motor changes should be fine. Swelling will take sometime to resolve . Some will have tiny scarring left. If it becomes an issue , a cosmetic concern , then consult with a plastic surgeon or dermatologist . Otherwise, leave it alone .