Good afternoon cupboy,
Welcome to the Apple Support Communities!
It sounds like you are trying to add music back to your iPod nano after restoring it.
Is your music library on a Mac or a Windows PC?
If you have not already done so, be sure to make a backup of music library:
Back up and restore your iTunes library on your PC
Back up your Mac with Time Machine
Are you able to sync a few songs or one playlist to confirm that your iPod is now working instead of the entire music library?
Use iTunes to sync your iPhone, iPad, or iPod with your computer
If your songs are grayed out
If the issue persists after trying the steps above, please reply to this thread and we'll do our best to help you!
Take care.