Grilled Chicken With Green Chile Sauce

4 chicken breasts, boneless, skinless
1/4 C olive oil
2 limes, juice only
1/4 tsp oregano
1/2 tsp black pepper
1/4 C water
10–12 tomatillos, husks removed, cut in half
1/2 medium onion, quartered
2 cloves garlic, finely chopped
2 jalapeño peppers
2 Tbsp cilantro, chopped
1/4 tsp salt
1/4 C lowfat sour cream