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.
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.