What Causes Irritation In The Sinuses?

Today I have had pretty irritated left sinus - I feel the irritation way back in my sinuses and I have been blowing my nose quite a bit to try to bring up whatever was back there. I finally blew out a very very odd looking discharge - It looked almost like a rock the size of pinky nail and had the consistency and look of brown dirt or mulch. It is now worrying me because I have never seen anything like it. My sinuses are still irritated but I can t get anything out. Is this type of discharge from nose normal? Thank you for your help!