The first day in a new job is read as a fresh start mixed with nerves. Dream books link it to wanting to fit in and proving yourself in an unfamiliar place.
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.