Preheat the oven to 350 degrees F. In a large bowl, mix together cake mix, sour cream, vegetable oil, buttermilk, eggs, apples and pecans. Stir until just combined.
Line a muffin tin with paper liners or spray well with nonstick cooking spray. Using an ice cream scoop, portion out evenly among 18 muffin cups. Bake for 17 to 20 minutes, until toothpick comes out clean.
Meanwhile, whisk together cream cheese, powdered sugar, vanilla and cinnamon. Add 1 teaspoon of milk and whisk. Add more milk, a teaspoon at a time, until desired consistency is reached.
Remove muffins from muffin tin to a cooling rack. Once cool, drizzle or spread with cream cheese glaze. If drizzling, place glaze in a plastic bag and snip a bit of the corner off then drizzle.