Gallstones are read as bitterness that has hardened into something solid. Folk tradition sees them as old grudges that now get in the way.
When this appeared in your dream, what were you feeling?
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.