my understanding is that B&N Nook App Store isn't available on other devices. I don't know if this will change in the future.
I would use Titanium Backup to backup your apps and data on your uSD card. Using the same uSD card, install the app from Playstore, then restore only the data. I dual boot, and a couple apps, like NoteEverything, keeps its data somewhere. And I end up backing up in stock and then restoring in CM10 or viceversa. But that only works with Playstore apps (rooted) and not with B&N apps.
Restore app and data from Titanium probably won't work.
You might be able to get some of you apps from Playstore.