Could it be something as simple as the Hold switch got turned on? I would try resetting it.
This will work for Nano's generation 1-5.
Toggle the Hold switch on and off. (Slide it to Hold, then turn it off again.)
Press and hold the Menu and Center (Select) button simultaneously until the Apple logo appears, about 6-8 seconds. You may need to repeat this step.
For a 6th Generation:
Press and hold the Sleep/Wake button and Volume Down button simultaneously for 8-12 seconds or until the Apple logo appears. You may need to repeat this step.
For a 7th Generation:
Press and hold the Sleep/Wake button and the Home Button until the screen goes dark. The Apple logo should appear after a few seconds, then the Home screen should appear.