Hi Phugoid Recovery,
You discribe a symptom of difficulty in breathing through your nose, relieved by use of Otrivin, a vasoconstrictor drug,and also your symptom is quite new.
Definitely a desciription points to nasal airway obstruction and sure it is a common symptom for a GP. You may indeed have polyps in your nose obstructing airways and they can be removed easily.But there are other diseases than polyps obstructing nasal airways, anatomical reasons after trauma for excample. Inflammation of the paranasal sinuses are a common cause for your symptom as well -and easily diagnosed.
But odema of the nasal mucosa, for some reason,may be propable cause of your symptom in my opinion.It may be caused by allergy or it may be so called. .vasomotor type, relieved by vasoconstricor drug for excample.
You definitely should go to a health check, to see if you have any other signs/proof of allergy and also anatomy of the nasal airways should be checked by visual inspection or by x-ray/ ultrasound/magnetic resonance imaging if needed at all. Go to a ear-nose-throat spesialist to have correct diagnosis and, then treatment.
Regards, Happy Harry