Hi @runner61627 welcome to the Head and Neck cancer group. This is where life has taken a side trip to the twilight zone.
The radiation in addition to destroying the cancer has also baked your mouth including the roof as well as the sinuses, salivary glands, tear ducts, and so forth. You most likely will have pain for several months which for many, Tylenol seems to work best.
Keep your mouth clean. Carry a toothbrush and some mouthwash or rinse with you in the car. You will still likely develop some mouth sores for a while despite the care you take.
Recovery from radiation is like recovery from a severe burn and perhaps worse. The healing time is much slower. If you measure improvement week over week rather than day to day, you will get a better idea of the recovery. It’s a lot to deal with especially if you were generally healthy in the past. You have to handle the pain and discomfort for a while but in time things will level out. Maybe not 100% recovery, perhaps 90% will be your new normal. Courage.