hi for your own safety id go to the accdent and emergecy department to be safe that it is not septacemia as if it is you will need to stay in hospital with an iv line have all the septicemia flushed out of your body as it could turn life threatning if goes untreated. I f the swelling continues and you do not decide to make a trip to the a&e then it may lead to survere life changes if it is septicemia it sound like it but if it is and it ony just started then it could always be treted at home on a cource of fluxacillin pills. but you mentioned swelling them seen severe to me best to gt it checked out, good luck best of wishes xx
At this point you need to go back to the ER, black and blue is never a good thing and tell this entire story to them again, Good luck!
I would go back to the ER since it is not getting better but getting worse. If it was a recluse, you don't want to wait for things to improve, you need to get attention fast.