9 Years Ago, I Had Oral Cancer. I Had No

9 years ago, I had oral cancer. I had no risk factors. I have never smoked and rarely drink alcohol. About half of my hard palate on the right side along with the upper teeth in the right quadrant of my mouth we removed by surgery due to cancer 14 years ago. I wear an obdurator. My dry mouth is a result of the radiation. I have post nasal drip due to allergies; however I am nor severely allergic to what I was tested for. I wonder if I have a sinus infection. I have no fever and rarely do. The light hurts my eyes when my symptoms are worse, and I have a headache. The PA at my EMT's recommended an oily kind of nose drops which helps the congestion to a degree. What else could I do to relieve these symptoms?