I stabbed him and I feel traumatized?

Well,some guy was messing with me and my girlfriend.We had tried to ignore him until one day, he tried again to bully us.This time I wasn't having it ,so i actually talked back when he was going on trying to act tough infront of his friends,(His friends said they weren't going to jump I'n the fight)He just succer punch me put of nowhere.I got him I'n a head lock and that's when i realize my girlfriend was taking hits at him too.I realize enough is enough,thus i backed off.He then hit my girlfriend when i backed off to take my box cutter out,he began to ran,and i chased him until he fell that's when i cut him from neck to chest.I remember seeing his chest as white, as white out.It was flesh and i just kept on afterwards.His friend then came after i cut him up and separated it.This happened last summer.I'm not trolling that's how people start I'n Ny.I am really worried since they live nearby .Recently he punched her and ran feel like i would kill him if i see him.Do you think He feels pathetic for his friends not getting I'n and for getting beat up when he was the one that started the fight?Please don't bring up police.Police don't do nothing until someone gets seriously hurt and that day i called the police and he didn't want to talk to the cops and since he was more messed up than me,hence nothing was done unfortunately.