Combine cumin, salt, and pepper; sprinkle over chicken.
Place chicken in an electric slow cooker; stir in onion, tomatoes, and chiles. Cover with lid; cook on high-heat setting for 3 hours. Stir in beans. Cover; cook on high-heat setting 1 hour.
Place 1 chicken thigh in each of 6 soup bowls; ladle 1 1/4 cups stew into each bowl. Top each serving with 2 teaspoons cilantro and 2 teaspoons sour cream.