He needs to see a vet.
It looks like he damanged his back bone to me. I had an iguana that broke it's back before and that's almost exactly what it looked like.
In the mean time, what is your cage like? He probably has limited mobility now so you should make the cage simple. If there is a water dish, be very very careful because if he/she gets stuck in the water it could drown - even if the water is very shallow.
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.