you will need to hard reset the phone. you will lose all data, but your phone will be back.
With the phone turned off, press and hold the VOLUME DOWN button, and then briefly press the POWER button.
Wait for the screen with the 3 Android images to appear, and then release the VOLUME DOWN button.
Press VOLUME DOWN to select CLEAR STORAGE, and then press POWER.
When asked to confirm, press VOLUME UP.