CashMoney, have you ever heard the rhyme "Stick and Stones may break my bones, but names will never hurt me"?
So the 14 year-old boy calls you names, and you punch him. That is assault. Forget what your principal said about the incident. You'll be in front of a real judge, in a real court, in the real world. DO show up to court, and when the judge asks you a question, DO remember that you'll make a better impression if you speak English (the real language, not the slang you've been typing here), show respect, and keep the language clean. I doubt self-defense will fly in court, but if you have no previous record, you may get off with community service, and you may even get your record sealed so this won't show up in the future.