Pistachio shells split open on their own when ripe, and in parts of Asia the nut is called the smiling nut, so it is read as openness and happiness.
Does the traditional reading fit your dream, or did it mean something else to you?
My Cosmic Code has a private dream journal. Write a dream down and the app picks out the symbols in it, shows what dream books say about them and, over time, which words recur across your entries. The journal is stored on your device only.