Lockscreen password forgotten

You'll have to put your device into Recovery Mode (If you can't update or restore your iPhone, iPad, or iPod touch - Apple Support) and then restore it to factory settings.

This WILL erase data on the device, however, it is the only way to make the device usable if you've forgotten the Passcode.

If your device is a media player iPod, not an iPod touch or other iOS computing device, connect it to computer that you use to sync it and run iTunes. It should not be locked after you eject and disconnect iPod. Or, do a Restore on iPod, from iPod's Summary settings screen in iTunes. This erases iPod, reinstalls its software, and sets it to default settings.