A guy who confessed to me

Recently I was confessed to by a guy from work who is one of my best friends. Even though we are good friends, I can't bring myself to think of him this way. He is not my type at all, he is not very talented in any particular area, and he's not very athletic, but he is a really good guy. It is the first time I was confessed to (I'm 21). I've never dated anyone, and I wasn't going to in the next few years. That's why I wasn't planning on starting a relationship with him, but, I have a lot of flaws which he knows about, and I feel like if I miss this chance, no one will ever accept me for who I am like he does. What should I do?