Ah! sorry I must have missed the pain in the forehead information.
Well, bottom line......if all the tests and X-Rays are normal...then they are normal, indicating no underlying disease process.
Prostate cancer can spread to the skull and occasionally presents with a boney abnormality of the skull, but clearly this has been excluded by blood tests and X-Rays.
It certainly sounds like Paget's Disease ion it's early stages, but yes, you can ask for a 2nd opinion OR monitor the situation for the next few months.