4 Answers

Reasons here...http://www.wisegeek.com/what-causes-a-swollen-nostril.htm

Best to check with your doctor.

SUPER GLUE?   
Sorry, I couldn't resist.  ROMOS and Benthere have given you the best advice.  I'll bet it is an allergy or common cold that has you stuffed up.   Hope you feel better soon.

When my dog wants a pooh,

The right side of my nose ( nostril ) collapses everytime I lie on my left side. I guess it's because my nasal passages are small and narrow; and there's really nothing there to support it open. I deal with that problem either by wearing  " Breathe Right " nasal strips , or  .......what  I mostly do is put tape near my nose, then  pull the skin closer to my ear and tape it down every night.That more of less keeps the nostril from collapsing. I think it's also a feature of aging, b/c some other areas of my skin are drooping. I've tried the rubber cones and supports that you put inside your nose, but they hurt and keep me awake.