ivy went away quickly, but after a week or so, I noticed an indentation about the size of my fist at the injection site. It's as if it ate my muscle, fat and skin (which is now discolored, ashy, and tender). Please help me figure out what happened and if there's something that can be done! Thank you.
This is most probably due to the intramuscular injection given - and less likely due to the medication. There are several complications associated with i/m injections including abscess formation, scar formation, contractures, necrosis , etc.
Consult your doctor , he/she would be able to clear out any doubts that you have and also give you a suitable treatment if required for the lesion.