sounds like and infection. he might have had a small wound that got infected. needs to go to vet, if not treated it could get into bloodstream and kill the dog. If you don’t have any money for a vet, you should not have a dog! they get really expensive quickly. thats what credit cards are for. take care of you pet or give it to someone who will. vet will give antibiotics( cheap) should not cost more htem 60 or 70 bucks
