Williamson initially suffered the injury in the second half of the McDonald's All-American Game on March 28 when he attempted to break a fall with his right hand.
The 17-year-old also missed out on the Jordan Brand Classic last Sunday because of the injury to his right (non-shooting) thumb.
A 5-star recruit, according to 247Sports.com, Williamson finished his high school career as the No. 1-ranked power forward in the country and third-ranked player overall.
The only two players ranked higher than him were R.J. Barrett and Cameron Reddish, and they'll both be joining Williamson at Duke in the fall.