What good will it come if you cut yourself? Nothing.
Cause you'll wake up tomorrow still feeling like total shit plus a serious injury. What you have to do is set things straight with your friend.
If it's your fault then apologise and give him a hug. If he/she's too upset to hear you, still talk honeslty to him and wait for his or her response.
You should realise that it's your life and you can do whatever the hell you want with it.
So why not doing things that will make you feel happy and satisfied with your self? why get lost in misery and self loathing? Wake up