What should I do?

In my 6th period class, I had made this friend. He was really nice and we got along really well. I have a boyfriend, whom I love very much. So, when we were walking out of class, his girlfriend saw us. She told him that he can't talk to me, or associate himself with me at all. Even though, he tried to tell her that we are just friends. I am not interested in him like that. What should I do?