Preheat oven to 425ºF. Place chicken on a baking sheet and season generously with salt and pepper. Bake in a preheated oven for about 23–25 minutes, or until it reaches an internal temperature of 165ºF. Allow to cool completely and slice into bite-sized pieces.
Place chicken, celery, apple, grapes, pecans, mayonnaise, and sour cream in a large bowl. Mix until well combined. Taste and add salt, pepper, and lemon juice if needed.
Serve immediately. Store any leftovers in the refrigerator.
