Your system would continue to work as long as you don't turn it off. So no matter what you do, keep it on until you restored your /boot
Recovering it should be straightforward, assuming you didn't put custom files directly to /boot.
Just reinstall the linux kernels using apt. Then manually run grub-install
with appropriate parameters. Finally, run update-grub
or grub-mkconfig
to recreate the grub config.
If the system is turned off, you can use live USB and chroot to it to properly install the kernel packages.