The upper left side of my back was scratched against a wooden bar in the basement. I could see a reddish line on my skin, a little above my left shoulder blade. Can this injury harm or injure my left lung?

Lungs are inside. Scratches on the outside of the body don't directly affect the organs on the inside of the body. Humans have skin, fat, muscles, bones between the outside of the body and the lungs, heart, and esophagus inside the chest.