Sunburn can affect the bark of JM on the sunny side of the trunk and ends up looking like this. Happens most often when a tree is suddenly moved into sun or the shade it is accustomed to suddenly disappears in summer. I have had this after defoliating in hot summer.
The other possibility is physical damage if it slipped off the bench and scraped that side of the trunk or something fell and delivered a glancing blow.
Any background info that might help narrow down possibilities?
Did the mark appear after purchase or was it already there when you got the tree? During winter? Summer? Could the tree have been exposed to more sun than usual at some stage? ETC?