Depending on how one views the meaning and importance of a concussion, a priest may or may not be necessary. Nothing in the Bible suggests that a concussion is only "real" if a priest is involved. Some confusion over this issue relates to work uniforms. Some professional athletes—here's looking at you, NFL—have become accustomed to obtaining concussions while standing near authority figures wearing black and white outfits. Those are referees, not priests, and the concussion is real even if the person in charge does not recognize it.
A strong desire to give others a concussion might be a sign of anger issues. If stress and rage have you itching to bust someone's skull, you don't "have to" give a concussion to anyone. A better target for that energy is some kind of punching bag. If you feel you need to
confess your anger issues to a priest, be careful you don't rush in with too much aggression; you just might give your concussion to the priest by accident.