my dog had that at one time, I took him to the vet and he had me clean his tail with betadine and apply an antibiotic ointment so Neosporin should be fine, but the best thing to do would be to take your dog to the vet to be sure what's causing it.
Could be a staph or yeast infection. Does it smell like corn chips? If so it is a yeast infection. If not probably a staph infection. Both can start from an allergic reaction. Having a vet check it would be best. Until yu can get th the vet clean it with some diluted hydrogen peroxide. (A 50/50 mix with water should work.) If it doesn't smell like corn chips put Neosporin on it. If it does smell like corn chips put organic cold press coconut oil on it.