Heat a skillet over medium heat. Add the rice (reserve the seasoning packet) and ground beef. Cook, stirring frequently, until the beef is browned. Add the water, corn, beans, and reserved seasoning packet. Bring the mixture to a boil then reduce the heat to a low simmer. Cover the skillet and cook for 15-20 minutes or until the rice is tender. Stir in the tomatoes. Sprinkle with the shredded cheese. Cover for 1 minute to melt the cheese. Remove the pan from the heat. Top with the sour cream and serve with tortilla chips.