I said yes, what will people say?

Okay, my best friend asked me to be his gf. I like him a bit so I said yes. I'm regretting it. He's cute, and he gas an awesome personality. we have some physical attraction but I can't imagine kissing him! And he's shorter then me. :/ I don't know what to do. It seems shallow because I'm scared what my friends will say mainly.... What do I do?