Bell went off midway through the first half on Friday as the Waratahs began life at the rebuilt Allianz Stadium with a 31-25 defeat to the men from the nation's capital.
The 22-year-old front-rower has been battling the injury since last year's Tests with England and was forced to miss the Wallabies' Spring tour to undergo surgery.
"It's a massive blow if that's the case," said Tahs coach Darren Coleman, when asked if the prop had re-aggravated the injury.
"We're holding out a little bit of hope but we're going for scans.
"He said it felt similar to what he did in the England Test, it's horrible news."
In Bell's brief involvement, he was able to set up teenage sensation Max Jorgensen for his first of two tries on debut.
Jorgensen, 18, crashed through the tackles of Rob Valentini and Allan Alaalatoa to score his side's opener, before a well-taken corner finish in the second half.
The wiry winger had been courted by NRL clubs, but looks set for a bright future in the 15-man game after becoming the Waratahs' youngest debutant since Kurtley Beale.
"Fear is an amazing motivator when you run that fast," Coleman said.
"Everyone has seen it, he'll go onwards and upwards, we're disappointed with the loss but I'm happy for Max.
"We always knew he was going to handle it and a few things went his way today and he got over the line. So that was awesome, and he's going to have a good career."
The loss was the Waratahs' 10th straight defeat at the hands of the Brumbies, but Coleman has already circled the return fixture in Canberra on April 1.
"We get them again in round six, we want to have another go - I don't think they're any better than us," he added.Â
