How can pain sensations appear to originate within the person's skull?
This question might be better handled by biology.SE. I think the short answer is that there are many pain receptors around the skull.

From wikipedia:


  The brain tissue itself is not sensitive to pain because it lacks pain
  receptors. Rather, the pain is caused by disturbance of the
  pain-sensitive structures around the brain. Nine areas of the head and
  neck have these pain-sensitive structures, which are the cranium (the
  periosteum of the skull), muscles, nerves, arteries and veins,
  subcutaneous tissues, eyes, ears, sinuses and mucous membranes.