A cough is the body trying to clear something stuck, read as wanting to say what you have held back. Dream books link it to irritation and a need to get something off your chest.
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.