In a medium bowl, whisk together the sour cream or Greek yogurt, lime juice, olive oil, ground cumin, chili powder, salt, and pepper until smooth and creamy.

In a large mixing bowl, combine the diced chicken, black beans, corn, red bell pepper, red onion, cherry tomatoes, avocado, and cilantro. Toss gently to mix.

Drizzle the prepared dressing over the salad and toss gently to coat all ingredients evenly.

Sprinkle the cheese over the top and add tortilla strips or chips if desired. Serve immediately or chill for 30 minutes before serving.