What do I do to stop this bully?

there is this kid who is a little weaker that me and he bully's me at the basket ball court with words.I really want to beat him up hard (I am a brown belt in karate)but I am to gentle and to afraid I will get in trouble.(this is in summer vacation so I can't tell a teacher).What should I do?Should I beat him up hard and get away with it?