Boufal is a doubt for Saturday's crucial home game with bottom club Watford.
"He couldn't train for three days now and it is still a bit swollen," said boss Ralph Hasenhuttl on Thursday.
"He hit his toe on the table at home.
"He ran into the kitchen and hit it on the table, something like that."
Asked if Boufal had any chance of facing Watford, Austrian Hasenhuttl said: "It will be difficult for the weekend."