This sticky about the shed cycle might be really helpful to you.

http://www.ball-pythons.net/forums/s...ad.php?t=28794

While it's possible the sounds you are hearing are due to loose shed over the nostrils, the fact is no one online can nor should diagnose what can be one of the symptoms of an RI. With any snake you take in as a rescue, with basically an unknown past, it's always wise to have a vet give it a once over and do a fecal float as well (will rule out any internal parasitic load).