I forked from repo "A". Named my repo "B". Pulled it down locally. Made changes, committed, pushed. Created pull request with a goal to merge only to origin/master of repo "B", but since it was a forked repo, default settings on BitBucket had it merged to repo I forked from, repo "A".
So now, the master of repo "A" has my changes, that were not supposed to be there. They were supposed to end up in a master of my "B" repo.
BitBucket has a "revert" button on pull requests but I am getting this message.

I tried "git revert -m 1 commit-hash" and am getting this error..

How can I revert that pull request and have repo "A" back to the state before the merge happened?
I went over many answers but there was no similar case.