Unlocking the bootloader and rooting your Galaxy Nexus is really only half the battle. There may come a time when you need need to lock everything back up, including that bootloader. Thanks to the Android team, we have the factory images that can not only fix a bootlooping or soft-bricked device, but make it look like you just pulled it out of the box.
1. Download the Android 4.0.2 factory images to your PC. [Download]
2. Unzip the file and its contents into your SDK/Tools folder (wherever your adb.exe and fastboot.exe files are).
*Make sure they are not in their own folder, but have all been extracted to Tools.
3. From within your Tools folder, open a command prompt (SHIFT + right click – “open command prompt here”):
4. Type the following commands, allowing each to finish before moving onto the next:
adb reboot bootloader
fastboot flash bootloader bootloader-toro-primekk15.img
fastboot flash radio radio-toro-i515.ek02.img
fastboot flash radio-cdma radio-cdma-toro-i515.ek05.img
fastboot -w update image-mysid-icl53f.zip
fastboot oem lock
5. Reboot your phone by highlighting “Start” and pressing the lock switch.
6. It really is as simple as that. Your phone is now back to a 100% stock, unrooted and locked state.
via Droid Life.