1st if you hit the ******* you lost already if he file police report and sue you you're screwed.... You cant use in the court that he give me permission to punch him, the judge will then tell you if someone tells you kill him you'll do it? he might utter if you do then your stupid leh :P lolz
2nd not worth my time
3rd you it wont hurt you hand if you punch someone? specially when you accidentally hit his head? I've been to a brawl when I was younger and after the brawl both my hand are swollen :-( for days...
walk away if you can this is the best you wont gain anything from fist fighting some more you may not know he could be a boxer or martial arts experts like the vid below