Want to move /boot from /dev/sda to /dev/nvme0n1p2

Hey LinuxQuestioneers!

I've noticed something very silly today.
I was farting about with my Debian (Buster) install and totally broken it.
So i did a full reinstall and now everything's really good and fun and lovely.

However, I noticed something very dumb.

My partition table is supposed to be:

/dev/nvme0n1p2:
- bootloader
- bootable flag
- /boot
- /swap

/dev/sda:
- /home

/dev/sdb:
- /[root]

What it actually is looks like:

/dev/nvme0n1p2:
- bootloader
- bootable flag
- unallocated
- /swap

/dev/sda:
- /home

/dev/sdb:
- /[root]

As you can see, the unallocated space on /dev/nvme0n1p2 is supposed to be my /boot partition.

My question is this:
Without reinstalling, how can I:
- move the /boot files from /dev/sdb1/boot to / and
- update grub to point to the right /boot partition

Thanks for any help!