What could cause a nostril blockage with a constant urge to sniff?

I have had a blocked right nostril for 6 years. I can't blow it out. For some reason, my body is constantly urged to "sniff" it, and I cannot breathe freely. Additionally, my nose feels like it's "collapsing" and i'm really aware of the nasal cycle. However, I've been to doctors and they said I did not have a deviated septum.