Cant get back into windows 10 when deciding to stop arch install
As a general comment, with Windows 10 you don't need to dual-boot in order to try Linux. You could instead install and use Windows Subsystem for Linux (WSL). If you want to also run graphical applications, upgrade to Windows 11 and ensure you're using WSL version 2.
To restore the Windows 10 startup, Run a Startup Repair. You will need a boot USB for Windows 10, or a Recovery media (if you have created one on your computer or another computer).
If this fails, you will need to do Repair Install Windows 10 with an In-place Upgrade.