In large skillet, heat oil on medium heat. Add diced onion and cook until translucent and soft, about 5 minutes. Stir in tomato paste and garlic and cook until garlic becomes fragrant, about 1 to 2 minutes. Add bison and brown, seasoning with salt and pepper, to taste. Once browned, add in diced tomatoes and black beans. Add chili powder, oregano, and cumin and stir to combine. Remove from heat and set aside.