I'm not Lance or Adarq, but I had a similar problem growing up.
You need to go see an allergist. It helped me, and now for the last 6 years or so I've had little to no problems with my nose being blocked up (except of course, the natural runny-noses you get in winter-time). But seriously, allergists can find out what's activating your sinus' issues most of the time.
I've also had friends swear by using NettiPots (spelling may not be right). One of my buddies is a pretty semi-successful country singer. He has baaaad sinuses and uses them to clean out his nose before he sings or records tracks.
Hope that helps.
Other than that, I'll let the other guys say if it will hinder your progress, but I would assume not too much...unless you just stop breathing altogether.