Based on personal experience I would guess you have something still under the skin like a rock, piece of glass or something. I wiped out a while back and proke open the skin on my elbo, after about a month It kept oozing and looking nasty so I was messing with it and out popped a little rock. Next day it was noticably better looking and completely healed up within the next week. It is amazing the problems a rock under your skin can cause.
If it doesn't start looking better quick You should definatley talk to a doc.