his best friend...

I broke up with my bf about 4 weeks ago. I now like his best friend. What do I do? His best friend and I are distant but are becoming friends. I can't talk to my ex and tell him either, or talk to my "best friend"cos she dated him and is dating my ex 4 days after the split. 
WHAT DO?😂😭
Editied -
Yh I've had a couple people say my "best friend" don't sound like one. That's y we ain't friends anymore 😂