Or you could just not give a forget. He'll forever have that medal knowing that he didn't even win it. It sounds dumb to do nothing, but really, what feeds trolls, again? That's right. Reacting.
Just, please, don't try too hard to act like you don't care, because it's really obvious when people do that.
If he confronts you about it or some stupid stuff because he's a pathetic troll, tell him to go forget himself and walk away.