It requires 2000 Reputation to edit every where. If you asked the question then you should be able to edit it as well as any answers you have posted. I can edit some of the answers of to questions I have asked but it is marked as needing moderation. Which takes time for the community to come and approve.
http://meta.stackoverflow.com/privileges
check 8th from the top.
http://meta.stackoverflow.com/privileges/edit