Hi.
I'm not sure what makes you think he asked you to the prom because there was no one else or that your friends pushed him to invite you. It may just be that he thinks you're cute and he's genuinely curious about what it would be like to go on a date with you.
But I hear you loud and clear--you don't want to go with him. If you really don't want to, then your evening--and probably his--will be ruined by your lack of enthusiasm. I would suggest that you tell him the truth and tell him right away so that he can ask someone else.
And do it gently--you probably want to keep his friendship. You will, indeed, risk hurting his feelings if you back out, but it will help you remember to take a little time before answering next year.
Have a good time--no matter who accompanies you to the prom!
