I always use a nasal dilator when I play. It is considerably more elegant that, say, a forefinger or a stone-lined mute. I find one comes in handy when you are sight reading through a really difficult nasal passage.
Most nasal dilators are singles. They come in two models, port and starboard. I prefer to use a compensating double myself.
Some players use guitar picks as nasal dilators, but my mother taught me not to do that in public. What a player she was!
Gotta go,
Cabbage