lidocaine, the painkiller combined with esiclene (20mg), would be something to consider as it kills the pain of esiclene (which, judging from the inflammation it induces, must be exquisite). unfortunately, i don't recall the ratio, but im sure there are places you can determine the "safe" amount to use....
of course, you have to exercise extra care to avoid infection by being extra careful with mixing....
one word of warning, as silver_shadow said, you will want to see if its an infection first (redness around the injection, inflammation, pus, etc) because the last thing you want to do is kill the pain around something that deserves to hurt (an infection in this case, you want it to hurt so you can do something about it rather than ignore it and possibly lose your leg or worse)...