Possible Skin Tag or Mole Infection

Hi, over the last year, I have noticed what appears to be a skin tag developing on the side of my leg (less than a quarter inch big), just below my knee.  About three weeks ago, I applied bloodroot to the tag to remove it.  A very small piece from the top scabbed over and came off, but that was it, and I stopped applying the bloodroot.  Now, about 3 weeks later, all of a sudden the skin tag has started to hurt.  Within a 2 day time period, it has turned almost completely black and my skin surrounding it is red, indicating an infection.  Because it is black, it now looks like a mole more than a skin tag.  It is definitely symmetrical in shape and doesn't appear to fit a melanoma scenario other than the fact that it changed color in 2 days and stings quite bad if pressed.  I'm planning on visiting a dermatologist tomorrow or within the week to get this checked out, but does anybody have any thoughts or information about this recent development?  I can take a picture if you'd like, but it appears to have a 24 hour wait period before the picture will be approved.

Thanks in advance!
-Matt