Best is to make an appointment at the Genius Bar of an Apple store
Apple Retail Store - Genius Bar
or send it in to Apple. See:
Service Answer Center - iPod
Sending it to Apple is not preferred since they may just retun it saying it is OK
Have you tried:
- Reset the iOS device. Nothing will be lost
Reset iOS device: Hold down the On/Off button and the Home button at the same time for at
least ten seconds, until the Apple logo appears.
- Reset all settings
Go to Settings > General > Reset and tap Reset All Settings.
All your preferences and settings are reset. Information (such as contacts and calendars) and media (such as songs and videos) aren’t affected.
- Restore from backup. See:
iOS: Back up and restore your iOS device with iCloud or iTunes
- Restore to factory settings/new iOS device.