When I first started using the Swift LT pillows, the inside of my nose had what you might call a burning sensation.
After a few days ( 5 or 6, I don't remember ) I had become desensitized. It was pretty rough at first, waking me up and such, but it was so much better than fighting the full face mask I had been using, I was motivated to put up with it.
I think it was the pressure inside my nose, kind of stretching it out.