cheating? should I tell him?

hey guys. I need some advice. I have a boyfriend of a year and I love him so much. after a party last night, me and a few friends were drunk and having a sleepover and one friend mentioned how horny she was and we started to kiss. the whole time I was thinking about him and this happened earlier in our relationship and he was cool with it but I don't know what I should do. it was purely experimental and didn't mean a thing, but I feel so guilty with the idea that I might've cheated on him and idk what to do. any advice?