Put water in a large pot and bring it to a boil. Then, add chicken into it and cook for 20 minutes or until done. Drain off the water, and after allowing the chicken to cool, chop it into small pieces. Next, place the chicken, apple, eggs, relish, onions, pineapple chunks, fajita seasoning, pecans, cilantro, celery, and mayonnaise, and toss together lightly.