A 23 yr old likes me?

I'm 16 turning 17 at the end of this year. Today I found out that this guy I worked with likes me. He didn't tell me, a guy who works with us told me. To be honest, I'm not interested in him in that way. I'm into older guys, but hes just not my type. I'm really nervous that he's gonna ask me out or something cause I'm really shy and when someone asks me out, I get all awkward, especially if my answer will be no, which in this case will be. I don't want to bring it up with him either. Like I said, I'm very shy, and being upfront about things is not my specialty. For all I know, he might not ever ask me out. He might just get over me or something. But, what should I say if he does ask?