if you check out some of the older posts in the archives you'll see some answers to your question i don't remember what the dealer did to help but i'm sure they should seeing it's under warranty...
Black 2k SE Performance/package
17x7 Konig-Caffeine's ,Stillen front spoiler and pop-cone intake,Aluminum dash kit,Remote starter,35% Tint,Aluminum Pedal Kit,APC Super white headlights and fogs and front and rear turn signals,Ventshade-ventvisors,Custom Front Grille,Stromung cat-back(in the mail)......
I had the same problem with my airbag. The front right corner of the cover didn't seem to fit right. I kept trying to push it back down. Then one day I lifted up on that corner and it came right up. I took it to the dealer and they had a new airbag in stock and replaced it right away with no hassles. The new one fits great. My suggestion is to complain. You don't mess around with ill-fitting safety devices.
2001 Sentra SE w/PP