Jennings, 20, broke a metartarsal during training on Monday and was due to have a further x-ray on the injury on Tuesday.
"It's disappointing for everybody because he's been a breath of fresh air since he signed," said Alan Knill, the Iron manager, speaking to the club's official website.
"I'm sure he'll come back with the same attitude. At first I thought he'd turned his ankle, but he said he felt something crack in his boot.
"We'd trained for 40 minutes before that and there was no problem and it's just one of those things."