May be a chronic fungal sinus infection, that may require antifungal nasal rinses and/or systemic antifungal treatment.
Could also be food allergy. My Brother gets a very, very congested nose from foods to which he is allergic.
Chronic Lyme, Bart., Gluten & Sulfite Sensitivity, Many Food/Inhalant/Medication/Chemical Allergies & Intolerances, Asthma, Gut dysmotility & non-specific inflammation, Lupus, Osteoporosis, etc.; G-Tube
Meds: Flagyl, Domperidone, Zofran, Claritin, Andrographis & other herbs, homeopathy, supplements, etc.