Should i do this? Is it Immoral?

Well see theres this one kid in school who thinks he is the best and he annoys me. he is always shouting over at me calling me names. he is a typical bully but the thing is he is fat AND ginger.! so after talking about it to my cousin i received a pair of Knuckle duster (Brass Knuckles) from him to do so damage. I dont plan on hitting him in the head more than once, but ill work the stomach well but i then taught that maybe this could caus damage and hurt him to an extent of being admitted to the hospital ?? what will i do because i think violnce is the only way here