1. Combine first 4 ingredients in a large bowl. Combine sour cream and next 4 ingredients in a small bowl.
2. Heat a small nonstick skillet over medium-high heat. Add cumin seeds; cook 1 minute or until seeds become fragrant and pop, stirring constantly. Stir toasted cumin seeds into sour cream mixture. Add dressing to chicken mixture, tossing well to coat.
3. Line each pita half evenly with lettuce and tomato; fill each with 1/2 cup chicken salad.
Note: If made ahead, cover and chill chicken salad until ready to serve. Assemble pitas just before serving.