Let it go?

So, one of my best friends is going to the mall on Saturday with a bunch of our friends. She really wants me to go, but there's kind of an issue. One of the people going was a really close friend of mine last year, but things are a little different between the two of us. If you're wondering, this friend is a guy. He and I were really close last year, but then things kind of change between him and I. He doesn't know it, but I kind of got upset with him at the earlier this year...kind of at the end of the whole school year. I wasn't really talking to him and I kind of avoided him. At the end of the year, on yearbook day is when I finally talked to him, really talked to him. Then other things kind of happened and I found myself upset with him again. There always is something I'm not telling, because I don't really want to say it...but I might let you know what it is...maybe... Anyways, my friend told me to come and I told her I would, but then she started telling me all who was coming and when she told me this guy was going I completely froze. I don't want to see him, but I don't want to let my friend down...besides I want to go...I just don't really want to go because I think it would be awkward with him there. I wouldn't know what to say to him and I'm also afraid that I'll ignore him and then he'll confront me about it, causing a big deal. Part of me wants to go, but the other part is telling me not to go. What do you think I should do? Should I just go and not let him get in the way, or should I just not go? Should I just let this all go and forgive and forget?