Heat the olive oil over medium heat in a large pot. Add onion, garlic, and carrots and season with salt and pepper. Cook, stirring occasionally, until carrots are tender. Stir in the cumin, crushed tomatoes, and vegetable stock. Bring to a simmer and stir in the quinoa. Simmer uncovered until quinoa is cooked, about 15 minutes. With 5 minutes remaining, stir in pinto beans and corn. Serve hot with avocado, cilantro, cheese, and limes on top!