A frowning face is read as disapproval, worry or a judgement you fear. Dream books ask whose frown it is, since it often mirrors your own doubt.
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.