In a medium casserole or Dutch oven dish, heat the olive oil. Season the pork with salt and pepper and cook over high heat until browned on both sides, about 2 minutes per side. Add the celery and onion and cook over moderate heat, stirring occasionally, until softened, about 7 minutes.
Add the diced chile, garlic, chile powder, cumin and oregano and cook, stirring frequently, until fragrant, about 3 minutes.
Add the chicken stock and bring to a boil.