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 iTunes purchases by:
Put in in recovery mode. There a plenty of instructions how to do that if you dont know what that is. It will wipe your ipod completely and restore it. means EVERYTHING will be deleted. but you can use it again. i hope you have itunes/icloud backup you so can restore it from backup later.
And the "connect to itunes" thing. well you can connect it, itunes will unlock the ipod again, but you have to enter the passcode. so thats not a option.