Hello and welcome to the head and neck group. Interesting that pain started up so many years out. Then again I was recently reminded of my own onset of osteoradionecrosis, bone death in my case the mandible. This can also happen in the shoulder, collar bone, and neck vertebrae from radiation of these areas.
Not a doctor but a very involved patient so I might suggest a CT or MRI to rule out a dying bone giving you all this grief.