A severed head is a stark image, read symbolically as a split between thinking and feeling, or the end of a way of thinking. It is not a forecast of harm but a sign of a sharp separation in your mind.
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.