You will need to Factory reset your phone in order to gain access. You can do this by turning it off then you need to press Volume Down followed by Power button. Wait for the screen with three Android images to appear and then release the Volume Down button.
Select Factory reset followed by Power button and you will have your phone unlocked but with applications removed. You can install them back via Store application.
Also, if the phone has a valid Internet connection you can enter the e-mail attached to the phone in order to receive the password. Once you do this, connect on a PC to the e-mail you've entered and then check for received password. Enter it on your phone and it will be unlocked.