What Are The Blood Scratches Found Under Skin?

I just went to a carnival and went on some thrill rides that involve spinning and going upside down. One ride had me pushed up against the restraints while I was lifted out of my seat upside down. An hour later I noticed these lines on both of my arms. They look like scratches that bled but under my skin. It is nothing on the surface. What is that called and how can I get that?