According to James, when he was a high school senior at the time Final Destination 3 premiered, he went tanning for a few months. But when he got a mole on his arm and didn't get it examined but finally did, he found out that he got skin cancer. After he got surgery to have it removed with a lymph node and extra skin, he was clear of cancer, but unfortunately, the scar didn't heal properly, which explains how he got the scar on his left shoulder.
Also, he points out that tanning salons are places that most characters-and real people-should not go to, preferably with the hazards of tanning beds.