If you have arm pain after getting the hepatitis B vaccine, pay attention to the surface of the arm for redness, swelling and color change to rule out whether there is an infection at the injection site. If the local redness and swelling is most likely due to infection, you can first apply a hot towel externally, which can promote the local redness and swelling to dissipate. If this situation occurs within 24 hours, you need to use cold towels, only more than 24 hours can use hot towels, but also with oral anti-inflammatory drugs, such as amoxicillin granules, is conducive to eliminating the local inflammation. During this period, you should pay attention to measuring the body temperature to avoid fever due to localized infection. If the pain is more serious, you can also apply diclofenac sodium gel on the local skin, which can well play a good role in relieving pain and swelling.