Williamson, making only his second appearance for Rovers, was stretchered off after an hour of the 2-0 defeat on Humberside.
"Obviously he'll get an X-ray and a scan," said Rovers boss Michael Appleton. "I don't think it is as bad as 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."