What Causes A Round Hard Bump On Right Side Of Head And Headaches?

I noticed about a week ago a pea sized round hard bump on the right side of my head, it feels like its on the bone. It does cause pain when I press on it, have been getting headaches for a few days that are relieved with Advil. The headaches feel like when I have sinus headaches and have to take zertec for a few days like pressure. The skin moves freely over the bump and it is not visible, both sides of my head look the same but I can feel the difference when touching both sides of my head in that same area. Any suggestions or input would be greatly appreciated, I do plan on seeing my pcp but just wondering what this could be, thanks!!