A month ago i had suffered a muscle strain from my tail bone, i also received pain killer on the day that i slipped that pain killer was given to me through injection at my back waist area near the buttocks after around i think 2-3 weeks my left butt cheeks i felt some bump or lymph nodes inside it's a bit painful when pressing it, some days it's small and some days it's like almost marble size some days also the bump is completely gone, could this had anything to do with the injection? is this considered as life threatening? i didn't get fever after the fall and even on healing days a month ago. Should i seek professional help?