If you punch a bully in the nose, maybe he’ll back down, maybe he won’t. Maybe he’ll punch you back. Possibly much harder (bullies rarely pick on anyone their own size; that’s what makes them bullies), possibly every day thereafter. What, you’ve never seen that happen? EVERY bully is a coward?
Maybe the only way to make your threat credible is to bring friends to back you up. Then maybe he gets HIS friends. And soon everybody is punching everybody else in the nose, and those who can’t (or won’t) fight are at the mercy of those who will and can. Until maybe (just maybe) someone who’s no good with his fists brings a gun to school. That’s “the great equalizer,” right?
Tell an adult. Maybe everything can end with NOBODY being punched in the nose.