What to do??

My bf and I have been in a LDR for about 9 months. Over the last couple of weeks we started taking about opening our relationship. We had both, on separate occasions brought it up, but this is the first time we had an honest, in depth convo. We talked about our reasonings, how we would manage, and what the rules would be. We reached an understanding...

Or so I thought. Fast forward two weeks, he calls me and essentially changed his mind. Over the last couple weeks, I had been hanging out with one of my guy friends. We kissed and then things escalated a little bit before he got really, really aggressive and I felt uncomfortable so I left. I also realized, hey, this open relationship thing might not be for me.

But now, I have this feeling of guilt. It’s not super heavy, but it’s there, lingering. My partner and I decided to remain exclusive, but, should I tell him about what happened?