You seem quite mature for your age miss lady bug.
You are right to turn him down as don't have same feelings but as others say say hopefully won't affect friendship.
Like say when you're young you're "in love" hundreds of times,but soon get over it.
I became best friends with a guy who rejected me when I was young.
I really fancied him and told him, but said sorry doesn't feel same. At first I felt embaressed but just got over it.
Then we started chatting again after then became really good friends, and actually I didn't fancy him any more after that!
He's probabaly just embaressed by it, rather than mad, so just try chatting to him as a friend again when next see him.