this guy I like had sex with my best friend

My best friend had sex with this guy months ago. They never went on a date or anything it was just sex. He reached out to me and we've been talking ever since. I really like him.. he's everything I've ever wanted. My best friend doesn't care that I'm talking to him because she's in a committed relationship. He doesn't care about her either. It's just a little weird for me... I don't want to let him go just because of this. He's perfect in every way & I see true potential with him. Has anyone else went through a similar situation or have any methods for looking past the situation with him & my best friend?