The bullet fired by a would-be assassin at a July 13 Trump rally in Pennsylvania came "less than a quarter of an inch from entering his head" before striking the top of Trump's right ear, said Jackson, a Republican congressman from Texas who served as physician to Presidents Trump and Barack Obama.
Five days after narrowly escaping assassination, Trump on Thursday accepted the Republican Party's presidential nomination for the November 5 election.
Jackson, providing what appeared to be the first public description by a medical professional of Trump's gunshot wound, said in a letter posted on social media Saturday that "the bullet track produced a 2 (centimetre) wide wound that extended down to the cartilaginous surface of the ear".
"There was initially significant bleeding, followed by marked swelling of the entire upper ear. The swelling has since resolved, and the wound is beginning to granulate and heal properly," he wrote.
Jackson said he had provided daily evaluation and treatment of Trump's wound since the shooting.
He said no sutures were required, but noted that due to the "highly vascular nature of the ear, there is still intermittent bleeding requiring a dressing to be in place".
"He will have further evaluations, including a comprehensive hearing exam, as needed," Jackson added.
Trump recounted the assassination attempt to a rapt audience on Thursday at the Republican National Convention in Milwaukee, saying that he was only there "by the grace of Almighty God".
"I heard a loud whizzing sound and felt something hit me really, really hard on my right ear," he said, a thick bandage still covering his ear.
"I said to myself, 'Wow, what was that? It can only be a bullet.'"
