You’ve lost your HEAD so you’ll need to recreate it. The simplest thing to do is this.
echo ref: refs/heads/master >.git/HEAD
Now you should be able to run other git commands and see where you’re at.
(Although, in theory, you could attempt to do git symbolic-ref HEAD refs/heads/master newer git versions don’t recognize a .git as a git repository unless it already contains a HEAD so this won’t work to create a new one.)