Your poor bunny looks like he's in a lot of discomfort. The open sore needs to be cleaned often so it doesn't develop an abscess. I just use a warm saline solution in a syringe to wash over the wound. If he gets an infection at this age, it is likely to become very serious right away. His little body won't have much stamina.
Please take the little one to a vet to have them make the ultimate decision a to what to do with his future. But if you do choose to give him a chance, some rabbits can live without the mobility of their hind legs. It is very time consuming as you have to help them with everything, and so you may have to decide whether you want to make the commitment. Again, this is only if your vet believes your rabbit will survive. In my experience with rabbits, it is unlikely he will regain use of his legs, but this depends on the severity of his injuries or deformity. Please please please, consult a vet.
Is this something you noticed just at the 11th day? Or had he always had mobility issues? Kits are normally able to crawl for some time before this, did he have troubles stabilizing? It is good to know if this is something he was born with versus something aggressive that started afterwards. (I can assume because of the wound he was born with this, but it is hard to tell)
I have been fortunate to not have to make the decision of whether or not to put one of my animals to sleep, mostly because rabbits turn from curably sick to fatally ill so quickly that there is not time, but I recognize that in some cases it is the most humane thing to do. I know it would not be an easy choice. I can only hope that consulting your vet will give you the understanding you will need to make an educated decision.
Please let us know how things turn out for you and your little bunny. I'm thinking about your little one, and you through this time.
ray: Don't know much about babies, but that doesn't look good.
