My boyfriend won't block his ex

My boyfriends ex was snapping him reminicing type things and also one sluttish snap and I found out about it .. confronted him

He said it wasnt a big deal and nothing became of it and if he wanted to fuck her he could've but he doesn't want to idk some stupid shit like that

But anyway they've known each other a long time and are "friends" and that's his excuse on why he wont block her.

I dont know what to do from here