Heat a large pot over medium-high heat. Saute pork in the hot pot until no longer pink, 5 to 7 minutes. Add onion and cook until transparent, about 5 minutes. Stir in garlic and cook for 1 to 2 minutes. Add cumin, oregano, salt, and pepper. Stir in pinto beans, diced tomatoes, and green chiles. Add chili powder and mix well. Pour in enough water to make a thin gravy.

Cover and cook, stirring often, until meat is fork tender, at least 2 hours.