Mild headache along my centre parting, for months.

For a long time, probably about eighteen months, I have had a sense of discomfort right along my centre parting. The pain is centred about two inches back from my hairline, and feels connected to the inside of my nose - sometimes, if I put pressure on the exact spot for a while, my nose starts to run. Because the pain is mild, I haven't taken any painkillers, but I'm starting to get annoyed with it. Any ideas what might be causing this, and if there is anything I can do to relieve it?