In a large non-stick pot, combine the lentils and chicken broth. Bring to a boil, reduce heat, cover and cook for 30 minutes. Add the tomatoes, onion, peppers, garlic, chili powder, cumin, and green chilies. Bring to another boil over medium heat, reduce heat, cover and continue cooking for 20 minutes longer or until lentils are tender. Add chicken, season with salt and pepper, and cook 5 minutes longer. Serve with cheese, avocado, and onion, if desired.