Im going out with a guy but im nervous?

well heres the thing... i had a friend called John who i met through my best friend Caitlin and well i asked him out last week and he said no because he'd just broke up with his gf and wasnt ready for a relationship, but today he asked me out and i said yes and now that we go out i dont know why but i feel nervous to go and meet him cause this was over facebook hed asked me. It's not as if we dont know each other. Why am i so nervous then..? i just have a feeling that maybe it'd be awkward? i want to make it work though. Any tips? Thank you.