Reset your iPod Nano
The following steps will allow you to reset your iPod Nano. Please make sure you know which generation iPod you have before you begin.
6th Generation iPod Nano:
If you have the most current (6G) model iPod Nano, then you need to simultaneously press and hold both the Sleep/Wake and Volume Down buttons for about eight seconds or until you see the little Apple logo screen show up.
1st through 5th Generation iPod Nano:
First, check to make sure the Hold switch is not turned on, as this will prevent all the other buttons from responding. Once you have verified that Hold is not activated, you can reset the older Nano by simultaneously pressing and holding the Menu and Center buttons until you see the Apple logo screen. It should appear after about eight seconds.
Regarding all Nano Models:
You may need to try a couple of times in case the reset doesn't work the first time because you may not be hitting the buttons at the same time. If after several tries it won't respond, Apple suggests connecting the iPod to your computer or another power source and then trying again.
For more information, be sure to check Apple's support site regarding how to reset any model iPod.
(Image Source: Apple.com)