My boyfriend kissed another girl what should i do

ive been going out with him for two months now and he kissed one of my friends one night. when i talked to him i let him give his explination he said that she always goes down on her self saying she will never get a boyfriend and things like that(which she does say stuff like that)so he just kissed her , it ment nothing stuff like that. i said he should of not done it because we were dating at the time. all of my firend expected me to break up with him but i didnt. should i have???????????