I Have A Painful Lump On The Back Of My

I have a painful lump on the back of my head above the hairline. I cannot get a good look at it, but it appears to be around one to three-quarters of an inch in diameter, is dark red with orange-colored puss coming from it. It feels like a small hot stone under my skin and causes severe discomfort. I've had it for over a week now. I can't tell if it is growing or remaining as it is. The pain keeps me from getting a full nights sleep. I have no change in eating habits or feeling anything else out of the ordinary (no loss of appetite, no vomiting, etc.) What could it be? Could it be a cancer? Should I get it surgically removed? If it is a cancer, could it spread to my brain, spinal collum, lymph nodes?