Preheat the oven to 200°C (390°F). Oil/grease a 38 cm (15'') baking dish. Set aside.
In a medium mixing bowl mix minced meat, salt, pepper, egg, bread crumbs, onion and Worcestershire sauce. Add cooked rice. Mix well.
Take a handful of the mix and form into a ball. Place in the prepared baking dish. Continue until all the meat mixture is finished. Bake for 30 minutes.
While the meatballs are in the oven, start preparing the sauce. In a frying pan, heat up the oil on a medium/high heat. Add onion and fry for 2 minutes, or until transparent. Add carrots, fry for 2 minutes. If using, add oregano. Add the diced tomatoes and mix well. Dilute tomato paste in water and pour over the sauce. Add salt and pepper.
Bring to boil. Turn heat down to medium and let it simmer for about 10 minutes, stirring occasionally.
Add sour cream and mix well. Remove from heat and set aside until needed.
Take the meatballs out of the oven and add the prepared sauce. Bake for another 40 minutes at the same temperature.
Serve with mashed potatoes, or a fresh salad. Frankly, can be eaten on their own as well. Enjoy!!!