Simply use the unprotected version of it you gave to friends or backed up.
Ok, I am guessing you did not particually do that...
Well luckilly for you it is impossible to protect maps, however you will no longer be able to use WE to edit the map (you will need to make a custom editor).
This is why you should always provide open source versions of your map to the public or distribute open source versions among trusted friends. It is very risky keeping the easilly editable version only to yourself, cause if your backups fail or something happens to you it becomes hard to maintain your map.
Incase you wonder why I have not directly helped you, it is cause this site does not support the discussion of repairing damaged maps.