Preheat oven to 425 degrees. Let pie crust stand at room temperature 15 minutes. Place pie crust in a pie plate, gently pressing dough into bottom and up sides; prick bottom. Bake 10 -12 minutes or until golden brown, cool completely.
Thinly slice green onions, set aside. Thinly slice half of the cheese. Grate remaining cheese. Set aside.
Place chicken in a micro-wavable bowl. Add barbecue sauce; toss to coat. Microwave on HIGH 3 -4 minutes or until mixture is hot, stirring after 2 minutes. Stir in 1/2 cup of the grated cheese and half of the green onions.
To assemble pie, line bottom and sides of crust with sliced cheese. Spoon chicken mixture into crust, spreading evenly. Sprinkle top of pie with remaining grated cheese. Pipe sour cream around edge of pie. Slice cherry tomatoes in half and place on top of sour cream, cut sides up. Garnish with remaining green onions.