Look for septic complications. from your description of the way the vaccine was given it appears that a hematoma may have been caused. There is likelihood of this getting infected. Severe pain on touching may herald the development of infection. I would suggest MgSO4 cold compresses locally to decrease the swelling and tenderness at least 3 times a day. Ibugesic suspension orally as advised for 3-4 days. A mild antibiotic like cloxacillin orally for 5 days. This will help in early resolution of the problem.