Boyfriends friend

A.B.

I have liked this guy for a very long time. He liked me back and we didn’t hide we liked each other. Well I guess his friend also liked me. I was friends with him as well. He was one of my better friends. I started to date the guy I really liked and my friend got mad. Like really mad. He started to say terrible things about me. Then he got really close to my boyfriend. To the point we’re my boyfriend didn’t have time for me. I don’t know what to do about the friend. Any ideas? Thank you so much ❤️