I need help with a people issue?

A person who i thought was my friend said i did something bad to my boss behind my back and i almost got fired!!!! worst part was he was the one who did it!!!!!!!!!!!!!!! I wanted to beat the $hit out of him but im not sure i know ill win the fight because he lost to a little 6th grader in a fight and he is in 10th grade =) but im a littel apprehensive because im kinda pacifist and even though i wont get in trouble im still not truly okay with the idea of actually hurting someone even though i could and should so any advice