Lomax came back for the All Blacks' win over Italy following a month-long absence after sustaining a freak knee cut which needed 30 stitches in the 35-7 warm-up defeat by South Africa.
The Italy game, and Thursday's clash with Uruguay, were meant to get him back into top shape for the quarter-finals, where the three-times champions will face one of the Pool B heavyweights.
"It looks like a small strain, we won't know for another 24 hours but he was looking OK," coach Ian Foster told a press conference.
It was an otherwise routine night for the All Blacks after they broke Uruguay's early resilience having had to wait 20 minutes to get onto the scoreboard.
"It was a really enjoyable game, pretty free-flowing. It took us a long time to breakdown Uruguay to be honest, they defended so well," man of the match Damian McKenzie said.
"But we managed to put some points on the board so I'm so proud of the lads. We've got to where we want to be, now we want to get better and move on to the quarters. I'm really excited for the week to come."
New Zealand will face Ireland, South Africa or Scotland for a place in the last four.
They are likely to finish second in Pool A and expected to take on top-ranked Ireland.
"I think we can work on the assumption we will finish second," Foster said.
"The thing about the draw is that first or second we kind of know when we got the draw, we knew it's gonna be a monster game."
The top four teams in the world - Ireland, France, South Africa and New Zealand - are in the same half of the World Cup draw.
"We know it's going to be a big step up coming next weekend," said Foster, after his team ran in 36 tries in the three group games following their initial loss to hosts France.
