Preheat oven to 450 degrees F.
Toss turkey with lime juice and season with salt and pepper.
Heat 1 1/2 tablespoons oil in a 10-inch heavy skillet over moderately high heat until hot but not smoking, then cook bell peppers, stirring, until crisp-tender, about 3 minutes.
Transfer to a bowl. Heat remaining 1/2 tablespoon oil in skillet over moderate heat and cook garlic, cumin, and oregano, stirring, 1 minute. Add the beans and cook, stirring, until heated through, about 1 minute. Season with salt and pepper.
Make 2 layers each of corn chips, sauteed peppers, beans, turkey, cheese, scallion, and cilantro in a 3-quart shallow baking dish. Bake nachos in middle of oven until cheese is melted, 6 to 10 minutes.
Stir together sour cream and jalapeno, to taste, and serve on the side along with salsa.