Good morning drufromottawa,
In order to remove a song or group of songs from your iPod nano, you need to sync it manually with iTunes on your computer, removing the songs you do not want from the set of songs you want to sync. See this manual for instructions on how to do so -
manuals.info.apple.com/MANUALS/1000/MA1624/en_US/ipod_nano_user_guide.pdf
Page 16 is the important part for your task.
Thanks for using Apple Support Communities.
Best,
Brett L