BRING first 4 ingredients to boil in large saucepan on medium-high heat, stirring occasionally. Meanwhile, mix meat, rice, bread crumbs, egg and cheese; shape into 16 (2-inch) meatballs.
ADD meatballs to tomato mixture; stir. Cover; simmer on medium-low heat 30 min. or until meatballs are done (160ºF), stirring occasionally.
REMOVE about 1/2 cup of the sauce; mix with sour cream. Return to pan; stir until blended.