Preheat the oven to 425 degrees . On a large, rimmed baking sheet, lightly spray the tortilla strips with cooking spray; arrange in a single layer. Bake until lightly browned and crispy, 6 to 8 minutes. Let cool.
In a large saucepan, heat the oil over medium. Add the onion, carrot and garlic; cook, stirring occasionally, until softened, 6 to 8 minutes. Stir in the chili powder and oregano; cook, stirring often, until aromatic, about 1 minute. Add the tomatoes; cook, stirring occasionally, until the liquid reduces slightly, about 5 minutes. Add the beans and stock, bring to a boil, reduce the heat to medium and simmer, stirring often, until the soup thickens and the flavors meld, about 20 minutes. Season with salt and pepper.
Let cool 5 minutes, then puree one-third of the soup in a blender. Pour the pureed soup back into the saucepan; stir. Divide among bowls. Top with sour cream and tortilla strips.