I believe editing questions works like editing comments. If so it gives you a bit of time to make changes. There will be a link that says something about editing and tells how long you have. If you click the word edit it will bring you back to where you can make changes. You can edit answers this way as well. I just checked that. :)
This is what it says: edit your answer (open for 9 minutes longer)and edit you answer or in your case it would say edit your question, is a link, underlined and blue.