Hit my head hard on the crown 3 days ago. was diagnosed with concussion without any imaging. also hit my head hard but barely developed a bump. is this normal? have had persistent headache since the hit?

Imaging is rarely needed after minor head trauma when the review of symptoms and exam are consistent with that label. Even minor head trauma can give rise to significant headache of and on for a week or more. Follow up with your regular doc and keep track of any dizziness, memory loss, brain fog, etc. and contact them when this spooks you.

If no loss of consciousness, and/ or memory loss, this was closed head trauma, not a concussion. Headache not unexpected If too intense or migraine like, visit neurologist