A little dope is good medicine.I had a similar sinus/cough in the November before Covid - felt like absolute dogshit however I was responsible for picking up someone at the airport for the get together at their ranch in the middle of Texas so I went and tried to be as sociable as possible That night one of the group said why don't you try this so I took 1 hit of some hash and within minutes I felt great with no symptoms.
I was up grooving for a couple hours while everyone else went to sleep. Not a recommendation just an observation. Still Covid free and not been sick since. Had all the shots and still alive and kicking. Drug and illness free ever since.