A thumbs up is read as approval given quickly and lightly. Tradition sees in it the wish for a simple yes, or a doubt about whether easy approval is worth much.
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.