After extreme exposure to cold a 42-year-old patient complains of headache in the left frontal lobe and the left upper jaw. Objectively: the face is symmetrical; left nasal meatus breathing is obstructed, and serous-purulent discharge is being produced; palpation of the suborbital area and further along the mucogi-ngival fold in the 24th, 25th teeth projection reveals slight pain. Percussion of these teeth is painless. The 24th tooth has a filling. The alveolar process mucosa has no visible changes. X-ray imaging shows decreased pneumatization of the left maxillary sinus. What is the provisional diagnosis?