git reset --hard
git pull will do two things: it does a
git fetch and then a
git merge where it merges branches that have been setup to be merged in your config.
So what you want to do is to undo the merge (undoing the fetch doesn’t make a lot of sense and shouldn’t be necessary).
To do that you can try using
git reset --hard to reset to a previous state. Use the git-reflogcommand to find the SHA-1 of the previous state and then reset to it.