My neighbor says he likes me, but I only like him as a friend. I'm really into someone els. What do I do?

Ok so today me my sister and my two friend Austen and Josh were chalking on my driveway. Austen says he has a secret and that only Josh knows what it is. The next hour he keeps mentioning he will tell us once he is about to go inside. Finally he says, "(name) ever since I met you I've liked you." he thinks I don't like him, and I kinda do but I really really like Josh. Austen gives my all the signs that he likes me, and Josh only a few. What should I do. Btw I'm 13, and I haven't told my mom yet.