The mole lives underground and works in the dark, so it is read as hidden activity and secrets beneath the surface. In dreams it can also stand for an insider, or a truth being uncovered slowly.
Has this come up in your dreams before? What was going on in your life then?
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.