My Bestfriend kissed my crush?

okay so me and this girl i like..and my two other friends..and we we went doing nothing kinky like that. but we were in a store and she walked away and so did my friend i thought they just went separate ways and going to buy something and im like "time to make my move". i followed her ending up seeing her and my best friend in a Deep make out...soo i need help dealing with this. she didn't see me but he did.. later he apologized and said she came on to him.. and she did. so should i keep chasing this girl.. and should i forgive my friend thanks in advance