Williamson will have a scan on Monday, following the scan the injury will be confirmed on the same day, once the results are ready.
New Zealand head coach Gary Stead said Williamson would probably sit out the final two games and prepare himself for the South Africa Test series."With the test matches so close as well and in the big scheme of things (they are) a higher priority I think we'll try and make sure he's right for that," Stead said.New Zealand lead the five-match series 2-0, with Williamson contributing 26 off 15 before retiring hurt in Sunday's second encounter, in which his side won by 21 runs.