Relationships?

So my boyfriend of a year and 8 months broke up with me about 3 weeks ago. It just wasn't working out and neither of us were really happy. Though I have been asked out and told people like me, I know I'm not ready for a relationship just yet. But, it seems like he is. He is hanging around one of my good friends a lot. While we were dating, I always feared they had a thing. Though she has something (not a relationship yet) with another boy, I still feel like they have something going on. I know we broke up but it would really hurt if they started dating. Not only because we just broke up but also because she is my friend and I would think that friends don't do that. I know I wouldn't. Should I just let it be and stop worrying or should I talk to one of them about it? And if I do, how?