What is the purpose of the mucous in the lining of the nose ?

the primary purpose of mucus is to coat the passageways of the nose, throat, sinuses, lungs and gastrointestinal tract and keep them from becoming dry. If these passages dried out, their surfaces could crack, potentially providing pathogens with an entryway into the body.

The purpose of mucous lining in the nose is to protect your sinuses and keep them moist.