In case you have forgot your backup pin, simply press the Power button and enable Data connection. Once activated, you can request a new pin on your email. Attempt this procedure then check your email. If the data connection activates successfully, you will receive a PIN that can be entered on your phone.
If none of this works, turn off the phone, press Power + Volume Up to enter Recovery, use Wipe Data / Factory Reset and you will have access to your phone.
Warning: This operation will delete the apps and custom settings.