Nasonex is a kind of steroid. the local use can prevent systemic side effect of steroid and it will need several weeks to get it's maximum effect. You should follow the dosage that your doctor prescribed.
Long term use of low dose steroid may affect your immune system.
You may have 2 problems: nasal septum deviation and nasal polyps.
You should know which causes your nasal obstruction. They are different and need different surgery approach.
Almost everyone has a nasal septum deviation. The indication of surgery(septoplasty) is depend on patient's feeling of nasal obstruction, the impact in daily life, if it become easily nasal bleeding, or it obstruct the natural sinus opening.
Alos, your may need to clarify if there are nasal polyps or not. If there are nasal polyps, it usually means your nasal sinus doesn't ventilation well,possible chronic sinusitis, and need surgical intervention(functional sinus scope surgery).
There are other manners to improve your nasal obstruction like local injection of steroid to your inferior turbinate or laser abrasion procedure.
Some patient come for surgery because of long term use of nasal decongestion drug.
Some old man will have difficulty in urination if they took nasal decongestion drug.
They need surgery to improve their quality of life.
Hope its helpful
Nasal steroid sprays, like Nasonex