How long can sinus inflammation last after infection is gone. Ctscan revealed inflamation but no infection. Still having head and face pressure & pain?

Sinus. Cat scan can't be sure that there is no infection. Might be low grade germ that previous antibiotic could take off or you stopped to soon. Alos fumes, tocacosmoke or allergies can also make iflammation. Are the canals to your sinus from your nose open?