He got jealous. It seems like (considering he’s a good guy) that he was under the impression that you two were the only ones talking and that eventually something would come out of it. Depending on how old you two are, I wouldn’t say he’s being childish. He clearly knows what he wants and that’s to talk to a girl who’s completely focused on him. I think now its up to you, depending on how serious you are about him, to decide what you want.