If the dog just has a pimple on his skin and has no other symptoms, it should be caused by two reasons. First, dogs have inflammation, which can be solved by taking anti-inflammatory drugs. The second is the acne that appears after the dog finishes the injection. Dog's body is inflamed: If the dog's body is inflamed, the lymph nodes near the dog's body will swell, and the acne caused by this situation can be solved by taking anti-inflammatory drugs. However, if there is no obvious relief after taking the medicine, you still have to go to the hospital for diagnosis, so as not to delay the illness. Second, if the dog finishes the injection and the drug is not absorbed in time, a pimple will form under the skin of the injection site of the dog, which will usually disappear automatically in a few days.