advice on my guy best friend

so basically my best friend that’s a guy will say stuff about the guy who i’m talking to. he seems to think that he’s gonna force me to do things and whatnot. i’ve done stuff with the guy before since we dated once and it didn’t work out and we’re trying to talk again and make things work. i’m 15 and the guy i’m talking to is 16. my best friend seems to think that he’s bad for me and is just going to use me but i really don’t think so. does anyone have any thought on why my best guy friend might be saying this stuff?