Dreaming of a concussion can be an indication that you need to change your life and focus on the things that are important. It is also a sign that you need to take more calculated risks and be more active in your life in order to reach your goals. It is not productive to have analysis paralysis in your waking life.
Dreams about injuries or medical procedures can sometimes be related to feelings of being overwhelmed or stressed in waking life. If you have experienced a concussion in a dream, it could be related to a feeling of being overwhelmed by your responsibilities or obligations.
Or it could be related to a fear of being hurt or a sense of powerlessness in some aspect of your life.