Boyfriend again...

So there’s this girl named Katy and she use to be really “good” friends with my bf. I found out that she sent nudes to him and all of that even though they supposedly grew up together and all that, yesterday he slid up on her video on Snapchat which irritated me so much so I confronted him about that and he told me that he’d stop doing that but this isn’t the first time he’s done it .. what should I do