Why do i keep seeing flashing/flickering lights after having a concussion?

Have it checked out: Not certain, it is possible that this is from irritation to the visual cortex from the head injury. However, one needs to be cognizant of a retinal problem such as a retinal tear that may have occurred after the impact. When one hears the phrase "flashing lights", that is usually a classical description for a retinal tear. You should have it checked out.