DMS burns off fairly readily after just a few minutes at a full boil. I'd say if you got a good 15-20 minutes of good rolling vigorous boil time, you're fine. Even so, unless your water is naturally high in sulfite, you should also be fine.
Beer so good, it's frightening.
2014: Seven Heavens Series One: Vilon, Mystic Melomel, Skeeter Pee.