Heat medium nonstick skillet over medium-high heat until hot. Add ground beef; cook 2 to 4 minutes or until browned. Remove beef from skillet; drain on paper towels.
Wipe skillet dry with paper towels. Return beef to skillet; stir in beans, tomatoes, chili powder and cumin. Bring to a boil. Reduce heat; cover and simmer 10 minutes.
Meanwhile, heat tortillas as directed on package.
To serve, sprinkle cheese evenly over tortillas. Top with beef mixture and sour cream; fold in half.