You will need to re-flash the firmware using windows device recovery tool, follow the steps as mentioned:
First of all charge the phone to ensure it has sufficient charge l otherwise you could brick the phone during the flash process.
:>Once charged up, you will need to get the phone into the boot-loader,
:>you need to press the power button and volume down until it vibrates.
:>Immediately after press the volume up button,
:>until you get the Nokia logo on top of the screen and keep holding until you see a red screen.
:>That is the bootloader, this may take a few tries.
:>Start up the windows device recovery tool, choose my device is not detected and quickly connect the phone.
You may need to wait a few minutes, be patient and once detected start the process. You will lose any unsaved data after this.
If you need additional help or want to reply to this thread , learn
how to join windows central.