The backup PIN is the one that gives you access to your phone. If you have an SD card attached, now it's the moment to remove it. Ignore the warnings while doing it because you will have to hard reset the phone to gain access again.
Follow these instructions and you should have access to the phone:
- Power off handset
- Press and Hold Volume UP + Volume Down + Home + Power key until Samsung logo appears
- Select Wipe data/Factory reset and press the Power key to confirm.
- Select Yes -- Delete all user data with the help of volume buttons and press Power key to confirm.
- Reboot and you should have access.
Insert the SD card and the content you had will be restored, but take notice that some apps and settings including photos and music might be deleted.