Lorie, first of all, I want to say that I always admire those who adopt a second-hand bird, because it is often not easy.
You did a fanastic thing by giving him a loving home. Who knows how much affection he was getting from a previous owner, probably not much. Maybe he does not even know how to be affectionate, how to give little conure kisses, nudge your neck with his beak, cuddle in your hair, etc.
With patience, maybe in several months, I think he will turn into an adorable and loving green-cheek. He probably needs to be tought how to be affectionate. I'd say work with him on daily basis, at least 3 x / day, 15 mins each session unless he gets bored sooner. Make those session fun for him so that he can't wait to play with you.
I wish I could help more. I am not an expert in parrot behavior... yet
Good luck!