Mixed feelings about long distance boyfriend’s actions

I am having mixed feelings about my long distance boyfriend kissing another girl. We discussed many times what we would do if someone kissed the other person and how we would react. My honest thought was that I wouldn’t care if he kissed another girl as long as it meant nothing to him and I did tell him that. Last night I received a text message saying he was coming back from a bar and a girl had kissed him and asked me if it was ok. I thought it was nice that he asked me coming back from the bar and I asked him a few questions about the kiss which he answered. I know he wasn’t saying it to hurt me, so I wasn’t angry with him. I was honestly happy he got kissed so he could enjoy himself since he had been stressed recently. However, the more time passes, I feel uneasy that he kissed a girl but I don’t want to bring the subject up to him all day long after telling him to not worry about one kiss.

He is also one of my closest friends, and I don’t want to lose him as a friend. He’s the person I talk to for everything. I wanted to make him not worry about the kiss and told him I was happy he told me, but I am still sad that it happened since the kiss was with another girl.