A raised bump on the back of a dog's neck may be caused by a tumor or failure to absorb the drug. If the dog has just received an injection, it is likely that the drug has not been absorbed. You can apply heat to the dog. If it does not disappear after more than three days. , it is best to take the dog to the pet hospital for treatment; if the dog has not received an injection and is in pain, it may be a tumor, and the dog needs to be taken to the pet hospital for examination and treatment as soon as possible.