I second the comfort thing. Also I would put him in there sometimes during the day with one of his favourite toys. Get him used to it so he doesn't feel scared or alone in there. Play games like peekaboo etc. or read him books in there. We also have a nightlight that
DS has had since birth. It is invaluable when we have to go away because it is something that never changes and brings him comfort. Basically don't push him as you want him to be happy sleeping in there. It is just a matter of him getting used to it really and that happens quicker if he is happy in there.
When
DS is resisting going to bed I always let him take whatever toy he is playing with eg. truck. He just has a play and is nice and relaxed and goes to sleep better (usually
lol!).