Scorch: verb: to burn a surface of so as to change its color and texture, to dry or shrivel with or as if with intense heat

From “The Shawl”: His chest was scorched with pain, and yet he pushed himself on. He’d never run so fast, so hard and furiously, but he was determined, and he refused to believe that the increasing distance between him and the wagon was real.

Now I came to understand that the boy was running very fast, so his chest was burning with pain but still he was not ready to give up the race with the wagon.