Sleep studies theorize that dreams are a way for the mind to process experiences that happened to the individual. Dreams help the brain to refine memories, allowing for us to remember those important events. New memories are stored, old memories refined to smaller clips or forgotten, to make room for new more important things that have happened to you.
I think the blood, scabs and clots represent the old memories. The things I've been holding on to, like tissue holding in blood and creating a bruise. Bad things, baggage, things that I was too angry to let go. The old blood is pouring out, the bad with it. I have excepted the pain a long time ago making the release painless. Those bad memories gone, pouring out the bad blood, the scabs are ready to be washed off and wiped away. The past of hate, anger and fear, ready to be let go and forgotten. A new beginning is now.