The midfielder, making only his second appearance for Rovers, had to be stretchered off after an hour during Rovers' 2-0 defeat to Hull City on Tuesday evening.
Initially it was feared that Williamson had broken his ankle but after assessment by the club doctor it is hoped that the injury isn't too serious.
"Obviously he'll get an x-ray and a scan in the morning," said the Rovers boss after the game. "I don't think it is as bad as what we first feared.
"He's come off on a stretcher, it is his ankle, but the doctor seemed to be reasonably confident that it won't be a fracture but I think he's got a problem in between the tibia and the fibula and the ankle joint.
"We'll get it looked at and we'll see how he is."
Rovers are back in action on Saturday when Leeds United are the visitors to Ewood Park. Tickets are on sale to those supporters with a database history of purchasing Rovers tickets. Priced from £19 for Adults, £12 Seniors and just £1 for Juniors.