Sore Knot on Fore Finger

I have been told according to the blood tests that I have OA.  However, I have a knot on my fore finger that came up looking like a blister because the skin was so tight and red.

 Then, the skin looked like a corn.  Before that could go away, it got inflammed and started to hurt, look red, swell and cracked.  It has a small dot in the middle that seems to be a small hole.

 I need to know what to do about the pain and swelling. 

Any help is greatly appreciated.