Boil a pan of water (salted) and add the rice. Cook for 8 minutes and drain before rinsing and draining again.
Heat the oil in a large pan and cook the onion, oregano and ground cloves for 2-3 minutes. Stir in the tomatoes (incl. juice) and rice and cook until the rice has absorbed the tomato juice and so it's a nice pink/red colour. Remove from the heat.
Cover the chicken breasts in a pan with water and bring to the boil, cooking for roughly 10 minutes or until when you think the chicken is cooked fully. Leave to cool before shredding the chicken and placing in the rice mixture with the sour cream and grated cheese. Turn the oven to Gas 3/ 160°C / 325°F.
Heat the tortillas by wrapping in foil and placing in the microwave or a low oven for a couple of minutes. Then, spoon in a bit of the mixture into the centre of each tortilla, fold in from both sides then the top and bottom. I suggest you making sure it stays that shape with a skewer.
Put them in an oven-proof dish and place in the oven where they'll keep warm whilst you make more. Simple ;).