Cover the chicken with cold water in a saucepan and add 1 teaspoon salt. Remove strips of zest from half of the orange with a vegetable peeler; add the zest to the water. Cover and bring to a boil over high heat, then reduce the heat to medium-low and simmer, uncovered, until the chicken is cooked through, about 18 minutes. Remove the chicken and let cool.
Grate the remaining orange zest into a large bowl; juice the orange into the bowl. Stir in the mayonnaise, sour cream, mustard, celery, nuts, chives, poppy seeds, 1/2 teaspoon salt, and pepper to taste. Add the apricots, if desired.
Shred the chicken, discarding the bones and skin, and toss with the dressing. Stuff a few lettuce leaves and some of the chicken salad into each pita.