If you have created a Restore Point earlier:
Go to Troubleshoot → Advanced options → System Restore
Pick a restore point before the issue started
Access Recovery Command Prompt:
Click Advanced Options
Go to Troubleshoot → Advanced Options → Command Prompt
bootrec /fixmbr
bootrec /fixboot
bootrec /scanos
bootrec /rebuildbcd
If fixboot says “Access denied”, run
bootsect /nt60 sys
Then try bootrec /fixboot again.