I have a knot that is VERY sensitive to the touch on the left side of the base of my skull. There is nothing on my scalp, so I know that it is internal. It burns and my scalp tingles in that area almost making my scalp itch, but I cant touch it. I have recently been sick with a sinus infection and was told I may have an infection in my sinuses on the back of my head. It is really painful.