there are many causes:
Trauma to the spinal cord between thoracic to lumbar-sacral region.
Any brain lesion/mass/tumor.
Any infection of the brain/brain stem(spinal cord).
Rabies.
Diabetic...
That depends on the nature of the injury. If it is a minor cut, then clean it twice a day with peroxide and apply an antibiotic cream; be sure to watch for signs of infection also. If it is a large...
It is possible your dog is suffering from vestibular disease. Have him checked by your vet. few things that cause this is ear infection old age or some pet medication.