Connect the iPod to your syncing computer and restore the iPod via iTunes. If iTunes asks for the unknown passcode place the iPod in recovery mode and then restore it. For recovery mode see:
Im not sure if you have to go through the process of a full restore so try step-1 First
Step-1: Restore your iPod from a backup. Normally after this it will ask if you would like to add a new password. (To restore from a backup Right-Click on your iPod in the left of iTunes and click restore from backup.
Step-2: If that dident work you are going to have to restore your iPod, if you are unable to use the restore button in iTunes as you have been locked out from entering the password wrong then you might have to use recovery mode. If the option is the go ahead without restore mode.
If you do need recovery mode there are instructions here, once in restore mode click the restore button
Place the iOS device in Recovery Mode and then connect to your computer and restore via iTunes. The iPod will be erased.
If recovery mode does not work try DFU mode.
For how to restore:
To restore from backup see:
If you restore from iCloud backup the apps will be automatically downloaded. If you restore from iTunes backup the apps and music have to be in the iTunes library since synced media like apps and music are not included in the backup of the iOS device that iTunes makes.
You can redownload most iTunes purchases by:
If problem what happens or does not happen and when in the instructions? When you successfully get the iPod in recovery mode and connect to computer iTunes should say it found an iPod in recovery mode.