Have you merged that branch from that PR that not supposed to be merged? Well, i already once, and i want to show how i got out of it.

What really happened?

On the project that this happened, there was two branches, that we will call here as main and parallel. Only changes from main can merge to parallel, and not the other way around. But, on that day, i have merged changes from parallel to main.

What do next?

So on the main branch, it had a last commit, that looks like:
8f937c683929b08379097828c8a04350b9b8e183

So i search "Git merge commit revert" and with all the things that i read, and the commit id that i got it, i had executed the bellow command:
git revert <commit_id>

And an error message was shown:
git revert <commit_id> alone won't work. -m must be specified

What is this '-m must be specified'?

So i searched deeper, and i found out this link on StackOverflow, that helped me a lot:
How to revert a merge commi thats already pushed to remote branch

if you run git log you will see the parents of the merge commit on the Merge prop, like this:
commit 8f937c683929b08379097828c8a04350b9b8e183
Merge: 8989ee0 7c6b236
Author: Ben James <ben@example.com>
Date: Wed Aug 17 22:49:41 2011 +0100

When you run:
git revert <commit_id> -m 1
You are saying that you want to come back like it was on 8989ee0.

And if you run:
git revert <commit_id> -m 2
You want to come back on 7c6b236 tree.

Thanks for the reading, and i hope that this can help you like it helped me.