What should I do?

Lia

My 14 year old baby has a bf who is 16 years old. I was watching his story and saw a TikTok video that he posted with a male putting a gun at a female’s vagina, a girl licking someone’s penis, a couple having sex and other sexual things. I sent a message to my sister instantly and told her to stop talking to this guy. I don’t want this guy to expose my sister to things she’s not supposed to indulge in. I don’t know the right steps to take to deal with this. I’m basically the mom figure in her life and I didn’t have that for myself so I’m not 100% sure what to do. I need some advice as to what I should do. Was I wrong to tell my sister to stop talking to him? I also told her how inappropriate the video was and I wasn’t forcing her to stop talking to him, but I think she should.