First a question from my side and i want to know how did you end up having this bruise
and since how long has it been there?
How you have described it seems you have a localised infection in a post traumatic hematoma
which is just a collection of blood which got infected.
If possible you may answer my query and than i would be able to help you in a better way. Meanwhile you may start taking painkiller as voveranSR 75mg twice a day after meals and start an antibiotic as well.
Also check if you have fever
Wishing you a speedy recovery
Dr . Gaurav