I rebooted into recovery mode with this command wirelessly via termux on my phone-

adb shell reboot recovery

I clicked on update from sdcard to see if I can flash su.zip but bunch of not found messages appeared.

Then I cleared cache and clicked on reboot to bootloader. It was stuck in that blank screen for a bit. So I switched off the power and turned it back on, but now it won't boot again, it's blank like the bootloader screen.

Edit: >!Fixed by flashing a ROM!<