Your answer had a typo. The OP fixed it. They didn't change anything important to the answer. You can see the edit history of a post by simply clicking on the "edited [timeframe]" above the name of the person who submitted the edit. In your case, that takes you to this page.
If you disagree with any edit, regardless of who submitted it, you can click the "rollback" button on that same page to revert it to an earlier version of the post.
This site and the network it belongs to is community edited. There are no rules for who can submit edits. Even anonymous, unregistered users can. We send all edit suggestions by users with less than 2000 reputation to an edit queue for review by the other users on the site (this edit was approved through that process).