No you don't have to buy a new phone you just have to force it in to safe mode by holding down the side buttons when you restart the phone until it gets into betting up then it will go to sage mode and then you will need to go to factory reset and completely wipe out your phone and start over
You have to reset your phone and restore your backup. You need to force restart it into recovery mode by holding the volume up and power button simultaneously. Keep holding the buttons until you see the Samsung logo then let go. When It boots into recovery mode, navigate to factory reset with the volume keys and select with the power button. The pin/password is not stored in the backup, so you would be able to set a new one. Write it down somewhere or at least make sure you can remember it.
