Can you get concussion from banging head afgainst af door?

Certainly: Any type of head trauma could cause a concussion, but please note, by definition, a concussion is loss of consciousness, loss or memory or a combination of both. Headache secondary to head impact does not qualify. However, maybe your head pain could respond to therapy. See your doctor.

Yes: Depends on force of impact, head position, and patient factors such as age.