Lawes had to be withdrawn just 15 minutes into the Challenge Cup last-16 clash, which Saints went on to lose 31-21.
And when asked about the injury after the game, Saints boss Chris Boyd said: "I suspect he's got a rather sore thumb.
"We know it's dislocated, the question will be whether it's fractured as well.
"If it's only dislocated, he might be alright for next week, but if it's fractured he probably won't."
Biggar could potentially face a Premiership ban, but Boyd insists it's another case of wait and see.
"Where's he going next week?" Boyd said, when asked how worried he was that Biggar would miss the Premiership trip to Bath next Saturday.
"Innocent until proven guilty, isn't it?"
Saints showed plenty of spirit at Kingsholm, coming back to 21-14 down after conceding three tries early in the game.
They kept battling with 14 men for almost half and hour at the end, but their Challenge Cup campaign was to fall at the first hurdle.
"You can't give a 21-point headstart," Boyd said.
"I thought we scrapped hard but at the end of the day, we got owned at the breakdown, offensively and defensively.
"We didn't adjust to how it was being adjudicated and we couldn't get our game going so credit to them.
"If I knew what it was the consequence of, I'd probably be a wizard or something.
"We knew what was coming so there was no surprise out there.
"They might have surprised themselves because they underestimate the quality of their backs - they've got a pretty decent backline.
"Everyone talks about their driving maul, which is a big part of their game, but they've got a pretty handy backline as well.
"It was disappointing for us really."