Preheat oven to 375 degrees F (190 degrees C). Spray a baking dish with cooking spray.
Bring a large pot of lightly salted water to a boil. Cook pasta shells in the boiling water, stirring occasionally until tender yet firm to the bite, 8 to 10 minutes. Drain.
Heat a large skillet over medium-high heat. Cook and stir beef in the hot skillet until browned and crumbly, 5 to 7 minutes; drain and discard grease. Stir salsa, tomato sauce, corn, and olives into ground beef.
Stuff shells with ground beef mixture; arrange in a single layer in the prepared baking dish. Sprinkle Cheddar cheese over stuffed shells.
Bake in the preheated oven until cheese is melted, about 20 minutes. Serve shells with sour cream.