There's this weird solution I've found for that error - try this first.
Restart the PC. During boot, go to the boot menu (boot devices), whatever it's called on your system. Usually it'll be accessed by pressing Esc, F8, F9, or F10, while the manufacturer's logo is on the screen.
Then choose "Windows Boot Manager", if available. If not, choose whatever drive Windows is installed to.
The upgrade should then complete, and you should be good to go.
You'll need to do this every upgrade (Feature Update to Windows, where the build and version numbers actually change).
Otherwise do the Reset and keep files, or if you have the option, restore point, or roll back to last build. These options are all on the blue screen, when you go into Advanced Options.