Dude, go to the doctor! This could be many different things, you need to have it checked out.
I had a similar problem a while back and thought it was a spider bite and it turned out to be celulitis ... Which can be life threatening if left untreated.
If it is a spider bite, some spider bits can get infected and become 'necrotic' meaning that the infection/venom will eat away and kill the skin tissue and leave a hole. Celulitis and do the same thing.
Symptoms of a cellulitis skin infection are:
- redness
- swelling
- extreme tenderness or pain
- skin that is hot to the touch
- red lines on the skin that run from the wound or sore to the lymph glands in the area.
Or maybe it is just an infected ingrown hair or something. But, you should defiantly get it checked out!
Good luck,
~ flutter :)