OK Birdlover,
Basically the idea is to immobilize the neck to give it a chance to heal. The neck vertabrae of the pigeon consist of small interlocking little pieces unlike the human spine which is something similar to a set of blocks, one on top of another with spacers of cartilage, held in line by a powerful set of muscles running parallel.
One possible solution requires about four or five pipe cleaners. You will need to go to a smoke shop to find them. They are basically wires about 6 inches long with padding. Cut a small piece of plastic about 7/8 inch by 3 inch, from a coffee can top or of something similar in stiffness. Bundle the pipe cleaners with scotch tape and then tape them to the plastic piece so about 3 inches of pipe cleaner sticks out with the other end flush against the end of the plastic piece.
Take some non-stick tape, the kind that sticks only to itself (any drugstore) and tape the plastic piece to the birds back slightly below the wings, around the body so it is firmly in place but not so firm that the bird can not breathe. The pipe cleaners should extend along the neck towards the head. Try to bend the pipe cleaners to the neck so they have a somewhat natural shape. Then take some lengths of cotton towel cut about four inches long, 1/4 inch wide, and very gently try to tie the neck to the pipe cleaners, being very careful not to tie them too tight or you will strangle him. Again, not to be repetitive, the idea is to immobilize the neck for about 4-6 weeks.
If this will not work, let us know and we will suggest something else.
The bird will need pain meds, check your medicine cabinet and get us know so we can talk about dosages. The bird will also need to be hand fed.
In behalf of the pigeon, we all extend our thanks for your willingness to help him in his time of need.