A transporter burn was the suggestion of a trivial injury.
When Ensign Muniz was gravely injured by the Jem'Hadar on Torga IV, in 2373, Captain Benjamin Sisko tried taking a look at his wound, but Muniz shrugged it off, telling Sisko he had worse transporter burns. Miles O'Brien noted that his statement was obviously an example of Muniz's bravado at work. (DS9: "The Ship")