If the phone has an active Internet connection you can follow the instructions from the related question to recover your PIN. Alternatively, I suggest you install Screen Lock Bypass Pro from Google Play Store. It will bypass the lock screen and will allow you to reset/remove your screen lock password, pattern or PIN number. If it doesn't help, you will need to perform a factory reset. Turn the device off, press Volume Up + Power buttons until the Recovery menu appears and select Wipe Data/Factory reset. Follow the on-screen instructions and restart the device after the process is complete.