Im A 40 Yr. Old Adult Male With Trouble Breathing

Im a 40 yr. old adult male with trouble breathing through my nose. I was in the shower one day and felt my nose was blocked on one side and it felt like something was stuck in it. So I preceeded to blow my nose hard and a round black mass as hard as a rock came out of my left nostril. Can you please tell me what it was and what caused it.