Here is Eric Cressey's excellent article,
Debunking Exercise Myths, Part I, which covers the use of weight belts.
Bottom line: Don't wear a belt for loads under 90% of 1RM. Increase your own "belt" of core strength instead and work on better lifting technique.
First recovery from the lower back strain with rest and ice. When you do go back to lifting, begin with mobility work and technique assessment. Fix what's wrong with your deadlift instead of relying on the crutch of a belt with poor technique.