Heat the oven to 425 degrees. Coat 24 mini muffin cups with cooking spray. Arrange 3 tater tots in each muffin cup. Bake for 10 minutes.
Using the bottom of a small glass or a spoon, press the tater tots in the muffin cups to form potato cups. Sprinkle with 1/4 cup of the cheese.
Meanwhile, cook the ground beef in large skillet over medium-high heat until thoroughly cooked and no longer pink in the center. Drain on paper towels.
Combine the ground beef, 2 tablespoons sour cream, ketchup, relish, salt, and pepper in a medium bowl.
Spoon into the potato cups; top with the remaining 1/2 cup cheese. Bake for 10 minutes or until browned and the cheese is melted. Cool on a wire rack for 5 to 10 minutes.
Gently remove from the muffin cups, running a small thin knife around the edge if necessary. Serve topped with the remaining sour cream.