You might be able to boot the system with a live cd and chroot into the installation and still fix the issue. I’ve done that to Arch and other distributions earlier but I don’t remember the recommended commands for Manjaro live cd chrooting just right now.
Edit: googling helps, you could try this if you didn’t reinstall yet:
[HowTo] Chroot from or into any Linux distribution
Although, I’d go with the manjaro-chroot command which handles steps 3-5 if I remember correctly.