I recently approved an edit (within the Suggested Edits review queue) by mistake. How can I retract/revert the vote?
Reviews can't be corrected once you've made a specific decision, unless you skipped it (skipped reviews can be revisited). Keep an eye on the review to see what the final outcome is by clicking on any of the review actions associated with the post within the Suggested Edits review queue's history tab (on the links within the marked column):
If your select action goes against what others have suggested, your incorrect action will most likely not make a difference. However, if it influenced others and you feel that a different action should have been taken, review the post outside the review queue and perform the appropriate action (either edit, retag, roll back, or leave it alone because it wasn't the end of the world).