I Received A Knock On My Chest Playing Soccer, And

I received a knock on my chest playing soccer, and the area has been hurting for 5 days. At first wasn't sure where I was hit, but yesterday I realized that the knock was directly over a vein. I also noticed yesterday that the area is slightly yellow in color. The pain occurs if I the area is compressed by deep breathing, or if I am using the left side of my body.
What should I do?