Lumps and redness in the arms after vaccination are usually normal if the area is small. It may be related to irritation caused by factors such as incomplete absorption of the local solution or fast injection speed or angle deviation, and can recover on its own without special treatment. If you take a shower, swim or exercise vigorously on the day of vaccination, or touch the vaccination site without cleaning your hands, it may also cause local redness, swelling, hard nodules and pain. The hard nodules at the vaccination site may not subside within 2-3 days, and may even cause symptoms such as increased redness, swelling, pain, or general discomfort such as fever, nausea, vomiting, and fatigue. In this case, it is considered that the patient is allergic to the ingredients in the vaccine or an infection has occurred, and the patient is advised to go to the hospital to clarify the cause. Also keep the vaccination site clean to avoid aggravating allergy symptoms or infection. Patients can apply hot compresses under the guidance of a doctor to promote blood circulation at the site of hard knots and speed up the absorption of the medicine and the dissipation of swelling. For patients with more serious hard nodules, wet compresses of magnesium sulfate may be required to relieve local skin and muscle tension, dilate blood vessels, promote blood flow rate and drug absorption, and help redness and swelling dissipate. It is also recommended to maintain a light diet during the treatment period, avoiding spicy, stimulating, greasy diet to aggravate the symptoms of local redness and swelling. Adequate rest and avoiding heavy physical labor and strenuous exercise to reduce the burden on the vaccinated limbs will help recovery.