Heat 1 tablespoon oil in a large Dutch oven over medium-high heat. Add chicken; cook 2 1/2 minutes on each side or until browned. Remove from pan. Cool slightly; coarsely chop. Add 1 teaspoon oil, onion, and celery to pan; sauté 5 minutes or until tender. Add garlic; sauté 2 minutes. Stir in water and broth, scraping pan to loosen browned bits. Stir in chicken, corn, and next 5 ingredients (chili powder through jalapeño pepper). Bring to a boil; reduce heat and simmer 45 minutes.
Stir in tortillas. Top with sour cream. Garnish with cilantro sprigs, if desired.