Unlock the lock icon on the nano?

Agreed, if the switch on top is to the right and you see orange, just slide the switch over to cover the orange. If this doesn't work, hold the center and menu buttons until a black screen with a white Apple logo appears. That will reboot the iPod. It should now not show that lock on the screen and allow full operation of the iPod.

Theres two locks on the nano, firstly the hold button on the top, its slides accross.
Secondly theres a screen lock that uses a four didgit pin code but that shouldnt be set withought you doing it.
Theres a master reset you can do on your ipod, slide the hold on top of the nano to lock then back again, then press in the menu and center button till the apple icon apears.
Theres a small booklet that comes with the nano explaining it. 🙂