:That happened to one of my snakes once... the vet poked the nostrils with a probe and pulled out this wad of.... stuff. Maybe dried mucus or shed skin or something. You could probably do that yourself, but obviously, be careful!
: : I would suggest that you very carefully & gently remove the obstructive matter (which is usually un-shed skin) with tweezers. If it doesn't easily come off with tweezers, you may want to apply water with a cotton ball to the area. This may be done a few times until the dried skin is loosened away from the current skin tissue.