I think I just accidentally voted to delete a first answer at: https://joomla.stackexchange.com/a/15237/120 in the review queue.
Is there any way I can undo this action or is this something only a moderator can fix?
I am quite sure you cannot delete an answer just by yourself. Other users get the change to review it as well - so do not worry.
The answer is still online and has not been deleted.