How to deal with a bully?

Today I was with with my friend walking in a promenade then we met a bunch from Grade 8 they're all bullies and kind of big and fat I'm not nerd but one of them keeps picking me on me... He came and slapped me in the face for no reason. and then started making fun of me I stayed quiet I don't mind that it's a small price then he told me do you wash your face my hand stinks? fu c h your mother that's when I got really mad I don't mind being slapped or being rubbed in the floor but my mom is very precious to me.. so I told him fuc h your mom too and he got mad and came to me i kicked him and ran away he runned after me for a while then my friend stayed there he stole his bike.... and came after me he followed me around the whole town and then I finally lost him and went home and he told me that he'd get me at school tomorrow with his bunch we're in the same school and he don't mind getting expelled cause he's going to be out of the school at the end of the year so telling the principal wont be much help...This guy is ruining my life he's 1 year older than me and probably stronger me and his nuts he doesn't care how other people feel he would probably try to pull out my eye like last year...