If you experience pain in your arm after the hepatitis B vaccination, pay attention to the surface of your arm to see if there is redness and swelling and color change to rule out any infection at the injection site. If the local redness and swelling is likely due to infection, you can first apply a hot towel externally, which can promote the local redness and swelling to dissipate. If this occurs within 24 hours, a cold towel should be applied externally, and only after 24 hours should a hot towel be used. It can also be combined with oral anti-inflammatory drugs, such as amoxicillin granules, to help eliminate local inflammation. During this period, attention should be paid to measuring the body temperature to avoid fever due to local infection. If the pain is serious, you can also apply sodium diclofenac gel to the local skin, which can be very effective in relieving pain and reducing swelling.