What Could Excess Nosebleeds With Clots Suggest?

Hi, I am a 49 year old female and yesterday I had a really bad nose bleed (right nostril) with a big, globby clot at the end. This morning, the same nostril started out of the blue, I hadn t even touched my nose. This was a much shorter time and a much smaller clot. What is causing this? After the nosebleeds, my sinuses feel sore or irritated.