In a breathless second period, Fiji were awarded a penalty try and Biggar - who failed a head injury assessment just 10 days ago - was apparently knocked groggy after an aerial collision with Liam Williams.
Wales were pushed all the way by a fired-up Fiji side at Oita Stadium before wing Josh Adams's try hat-trick underpinned a 29-17 Pool D success.
"We will review this one and look forward to the Uruguay game".
Wales are hopeful fly-half Dan Biggar and centre Jonathan Davies will be fit for a likely World Cup quarter-final against France.More news: Will speak to RBI Governor, Nirmala Sitharaman assures PMC bank depositors
Gatland said he had been forced into more changes than he wanted in the backline because of injuries sustained during the Fiji match, most notably to flyhalf Dan Biggar and centre Jonathan Davies.
"The message to the players against Uruguay is that the door is not shut". He was symptom-free the next day, which was great.
"The medics have spoken to a number of people during consultations", he said. "He is just going through the HIA protocols at the moment". He's being monitored as well.
"It had a bit of swelling and he's been icing it regularly".
"He gets a bit more time so hopefully that keeps improving over the next few days".More news: Epic Games CEO supports freedom of speech despite Tencent's stake in company
France finished as runners-up in Pool C following the cancellation of Saturday's game against England due to the approach of Super Typhoon Hagibis.
"We knew from the start that this was a possibility", Gatland said.
Scotland will be anxiously watching reports on the incoming typhoon, as they will be eliminated if Sunday's game is cancelled and marked down as a 0-0 draw, giving them only two points.
The disappointing result for the Fiji team was balanced by the joy of his daughter's birth - who he says will "definitely be a Fiji fan herself".
Warren Gatland says he feels sorry for Italy.More news: Federation Internationale de Football Association will 'stand firm' on Iranian women's access to all matches
"We didn't panic. We knew if we stuck to our process we would pull them back in, but when you see some of them running around it is a tough one to defend". Argentina were a very good team before but if you're playing New Zealand, South Africa and Australia week-in week-out it's going to help you and we're the same.
- Korea threatens to resume nuke, long-range missile tests
- Trump says will meet Chinese vice premier Friday
- Queensland councillor asked to quit over appearance on The Bachelorette Australia
- Max Scherzer baffles Dodgers, Nationals force Game 5 in NLDS
- Turkish President Announces Offensive Into Northern Syria Has Begun
- Newest 'Sesame Street' Muppet has a mom struggling to overcome addiction
- Court: Deutsche Bank Does Not Have Donald Trump's Tax Returns
- Sony confirms the name, launch time and features of next-gen PlayStation
- NASA chief set to tour SpaceX factory
- Trump to meet with top Chinese trade negotiator Friday