A rotten egg stands for a promise or idea that has gone sour from waiting too long. Dream books also connect it to an unpleasant truth that cannot stay hidden.
Where in your waking life have you met something like this lately?
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.