For the meatballs: Preheat the oven to 400 degrees F. Spray a rimmed baking sheet with cooking spray.
Melt the butter in a small saucepan over medium heat. Whisk in the hot sauce, remove from the heat and let cool to room temperature.
Combine the chicken, breadcrumbs, celery, egg, onions and 1 teaspoon salt in a large bowl. Add 2/3 cup of the cooled hot sauce mixture (reserve the rest) and mix to combine. Form the chicken mixture into 2-inch meatballs (about 18 total) and place them on the prepared baking sheet.
Bake until cooked through, about 20 minutes, brushing the meatballs with the reserved hot sauce mixture during the last 8 minutes.
For the sauce: Combine the sour cream, mayonnaise, blue cheese and vinegar in a small bowl. Season with salt and pepper.
Serve the meatballs with the sauce and celery sticks.