The pain in the buttocks after the injection is generally considered to be caused by drugs, because some drugs are particularly irritating to the muscles and may cause pain in the buttocks after the injection, such as penicillin and other drugs, the pain in the buttocks is very obvious when the injection is given and will be painful for some time after the injection. It is also possible that the pain is caused by bleeding at the eye of the needle after the injection. It is possible that the blood supply in the muscle is very rich after the needle is pulled out because of the injury to the blood vessels or the place where the needle was injected, which causes pain at the eye of the needle. If the patient’s pain is particularly pronounced, you can apply a hot towel topically after a day, which may help to eliminate the pain.