I’m so sorry this happened to the little guy. Please pick him up from the Vet and find another vet. I’m not usually that blunt about seeking a second opinion, and I can only go by what you have told me, but it is far too soon to give up on your bird. With many Vet clinics owned by corporations these days, they tend to have vets for different specialties, but for birds, it is often an exotics Vet, who may not have much experience with birds. Try to find an ABVP Board Certified Avian Vet. You can use our locator on this link, and on the same page, there are links to search with ABVP and AAV: https://lafeber.com/pet-birds/find-an-avian-vet/
As a Veterinary technician as well as a wildlife rehabilitator, I have worked with many birds with head and spinal injuries. Birds have an amazing ability to recover from these injuries. Someone brought me a parakeet that had flown head first into something. He was paralyzed from the neck down. The Vet put him on an anti-inflammatory for 10 days, but there was no improvement. I set up a cage to accommodate him – he could pull himself around by his beak. After a few months, he regained use of his wings, which we discovered when he suddenly flew! It took a full year, but he was eventually able to walk again. I had a similar experience with an African Grey that flew into a brick wall. I can’t remember the time frame, but he also recovered fully over a period of months. Those are only two examples of the full recoveries I have seen.
I hope they have your bird on an anti-inflammatory and pain medication. If he is eating on his own, then there is hope. You need to configure a cage for him where he isn’t on wire, and he has sturdy food and water bowls that he can easily eat and drink from. Check small pet or reptile dishes at the pet store because they are often shallow, heavy and many are made from ceramic. Ceramic is fine as long as it isn’t cracked. For the floor, a towel may be best – one that doesn’t have loose looping or threads so he doesn’t get his toenails caught. Find a plush dog or cat toy for him – this is something he can use to prop up against. You will have to change the towel at least twice a day, and keep his feathers clean – he will end up with poop on him, so just wipe that away gently with a paper towel damp with warm water. You don’t want his vent area to get raw. If he has use of his wings, do not clip them, but also be careful – you don’t want him to fly and get injured. Give him some time for the swelling to go down, and then encourage exercise. Hopefully you can find a Vet with experience with these type injuries, who can help guide you. But as you have found, there are many stories of birds that have recovered, so you may be able to learn from those owners. Please feel free to reply if you have more questions, and make sure to put my name on the subject. I definitely want to hear back from you when he starts to recover and look forward to the day when you tell me he is walking and flying again!