Place walnuts in skillet. Over low heat, toast walnuts about 3-5 minutes until fragrant. Remove for heat and let cool. Then place the toasted walnuts in food processor or blender until finely chopped. Cut nectarine in half and remove seed. Cut up fruit; place in blender or processor and liquefy. Pour pureed fruit into a large saucepan. Add honey, brown sugar, lemon juice, cinnamon and ginger. Cook on low heat for 8-12 minutes until thickened. Stir nonstop once comes to a boil. Remove from heat and let cool. Rinse chicken and pat dry with paper towels. Once the sauce mixture is cooled place the chicken in a large zip-locking bag. Add mixture and toasted walnuts. Remove most of the air from the bag and make sure all the chicken is covered with the sauce. Refrigerate 1-2 hours before removing from marinade and grilling. Discard marinade. Then grill until done, being careful to avoid burning.