You can change the primary profile name by following the instructions below.
NOTE: Your NOOK HD/NOOK HD + must have software version 2.0.6 installed before proceeding.
1. Tap the Primary Profile's NOOK in the upper left corner of the Home Screen.
2. Tap Edit Profiles.
3. Tap the Primary Profile icon.
4. A pop-up menu will appear; tap Change name.
5. Enter the desired name; tap Done.