If a cat has a hard lump on its body after the injection, it may be that the drug has not been absorbed. Owners don’t have to worry. You can use a hot towel to apply to the cat’s affected area to help relieve the symptoms. Sometimes allergies can also cause this condition in cats. You usually take care of your cat. After the vaccination, you can stay in the pet hospital for 10-15 minutes. If the cat has physical abnormalities, seek veterinary examination and treatment immediately to avoid delaying the condition.