What do I do about this boy?

Well my friend and I met this guy a year and a half ago. She lived in the next town over and didn't come over a lot. I started to hang out with the guy, and we became really close. My friend knew I liked this boy, and so did she. I was a stupid idiot and I hid the crush fearing it would ruin my friendship with the boy. A while later he gave me a letter telling me that he liked me. I stopped hanging out with him after that. A few months later, me and my out-of-town friend went over to his house. (he's my neighbor) Finally we started hanging out again. My friend-girl( Let's call her nikki) was hanging out with us too. They got really close and now they're going out. She knows EXACTLY how i feel, and now i feel betrayed. I still really like this guy AND he's my best guy friend. My mom says just wait. WHAT DO I DOOOOOO?????