Skin tumors are common in dogs, but it is often impossible to determine what sort of tumor it is by appearance alone. It may be a hematoma or an epidermal inclusion cyst, but the only way it can be truthfully established is by way of a biopsy. Take the dog to a vet for proper diagnosis.
what i think you should do is take the dog to the vets and see what they say because i have a dog at two and i have had lots int he past non of my dogs have ever had lumps so take it to the vest and see what they say ok wish the best xx
my aunt had a Bassett hound named sofie. she had the same thing it ruptured alot. we took her to the vet and they said it was a tumor later on she had to be euthanized. if you want your pet to have a chance of living you need to have it looked at.