In 2017-18 Devin Booker missed some time because of a broken right hand – his shooting hand. It seems that he has either re-injured that hand, or that after a busy summer it is still irritating him and reached a point that surgery is the next option.
This is nothing to worry about.
Regardless of if this injury is one that he has had to deal with all offseason, it is something that crept up on both he and the Suns, or it happened playing a pickup game on Sunday morning, there is absolutely zero doubt that prior to signing his max extension (of 5-years and $158 million), the franchise did a full body scan of Booker, meticulously prying over every formerly injured nook and cranny, as well as every joint and muscle that could possibly become a problem for him in the future.