My screen had a lock on it and i forgot the code for it now i cant unlock the screen how do i unlock it?

1. Plug the iPod into the primary computer linked to that iPod, the first computer you synchronized it with unless you have designated another computer as the primary computer.
2. Open iTunes and sync the iPod as normal.
3. Remove the iPod, following the normal removal procedure. The iPod unlocks automatically as you remove it.