Preheat the oven to 375°F. Spray a 9×13-inch glass casserole dish with nonstick spray.
In a large bowl, combine the pinto beans, chopped green chiles, taco seasoning, and 2 cups of shredded cheese.
Place a tortilla on a flat surface. Add 1/8 of the bean mixture down the center. Roll tightly and place seam-side down in the prepared baking dish. Repeat with the remaining tortillas and filling.
In a medium bowl, whisk together the salsa verde and sour cream until smooth. Pour the mixture evenly over the enchiladas. (This will feel like a lot of sauce, but go with it - the sauce thickens and reduces slightly as it bakes.)
Top with the remaining 2 cups of shredded cheese. Cover the pan with aluminum foil and bake for 30 minutes. Remove the foil and bake uncovered for another 10 minutes, until the cheese is melted and bubbling.
Let the enchiladas rest for 10 minutes. (This helps the sauce thicken slightly and makes the enchiladas easier to serve.) Top with pico de gallo, if using, and serve hot.