Believe it or not, a spider bite can be very, very dangerous!!! My husband got bite and did nothing about but scratch. Over a 2 week period it got larger and he woke up with a boil looking thing on his arm. It popped and started leaking this greenish-brown oozey suff. The next morning i could smell it one room away. YEP, he sure did go to the ER then. It smelled like rotten meat!!!(sorry so gross) But, it's true. His arm was actually rotting inside from the infection. The doc said that it happens all the time and people let it go, and loose their arm. Get it checked please. I saw what he went thru and it was bad! Good luck and let us know how it goes k! -Marebear74
Maybe an infection, a boil you should see adoctor to be sure skin infections can go bad fast and they are painful.
I would say spider bite and from the soudn of it I would get it checked out right away! If it is a spider bite it gets worse before It gets better and the sooner you start treating the better.