Post treatment - coughing, sneezing, chest pain

I am 4 months out from treatment. Had my 90 day PET/CT 30 days ago and all sign of the disease I had was gone. But, they found some stuff in my lungs that concerned them - inflammation or more cancer? They don't know. Get scanned again in 30 days. But now I am experiencing coughing when I drink some fluids, little sneezing fits and occasional flu-like chest pain in my lungs. I don't eat anything solid yet, so I'm thinking maybe some of the fluid is making it into my lungs and casuing infection. But I am curious if any of you have been where I'm at and can chime in and have any ideas about what I should do.