Waghorn joined the Tigers on transfer deadline day in August on a deal set to run until the end of December.
The England Under-21 international has been nursing the injury for several weeks and the problem looks set to rule him out beyond the end of his stay on Humberside.
"He has been brought back for assessment and he is going to get some treatment here because it was a lot more serious than first thought and it wasn't really repairing," said Leicester assistant manager Craig Shakespeare.
"We have had him scanned and we will treat him on a week-to-week basis here. He probably won't be fit before the loan finishes anyway."