What should I do if there is a hard lump on my baby's arm after getting a shot?

Patient's question:

No

Doctor's answer:

Hello, it might be caused by a boil. Generally, it presents with skin redness and swelling, and in severe cases, fever may occur. Before it softens, you can apply fish oil ointment externally. Pay attention to local hygiene, and take anti-inflammatory medication to prevent infection.