Ellis limped off just before half-time following an incident that involved Ospreys lock Ian Evans.
Both Evans and his high-profile colleague, Wales Grand Slam star Gavin Henson, could now attract the scrutiny of match citing commissioner Bill Dunlop.
Henson missed two penalties and two drop-goal attempts as Pool Three leaders Leicester triumphed 17-15 thanks to an 84th-minute Dan Hipkiss try that fly-half Andy Goode converted with the game's final kick.
Henson's most notable contribution was to become embroiled in a 19th-minute incident with Tigers prop Alex Moreno.
"I will wait until I see the video," was Leicester coach Pat Howard's solitary comment on both the Henson incident and Ellis episode.
Howard's more pressing concern was the ligament problem suffered by Ellis, who produced a sparkling performance when England beat Samoa 40-3 last month to put himself in pole position for Wales' February 4 visit.
"The citing commissioner has got to make his decisions, and I will live with that.
"Harry looks as though he has copped a significant injury, and the injury is the only thing we can control," added Howard.
"I think it is unlikely he will be available for a while. We would expect to know more in the next 24-48 hours, but hopefully the scans will not show too much damage."
Leicester centre Ollie Smith and lock Louis Deacon were both sin-binned during a fractious affair, but Leicester's last-gasp triumph put them back on top of Pool Three prior to their final European fixtures against Stade Francais and Clermont Auvergne next month.
The quarter-finals now beckon for Tigers, and Howard said: "It wasn't our best day at the office, but I thought the players' commitment was fantastic.
"We are in a lovely position now, but it is by no means sealed and settled.
"At 15-3 down, I thought we were in trouble, but a great captain (Martin Corry) brings people together.
"It wasn't going to be easy, away against the reigning Celtic League champions, and I am very happy to come out of it with a win."
British & Irish Lion Corry added: "We didn't play very well, but we got lucky. Victories on the road in this competition are hard to come by, so we will certainly take it."
Austin Healey, who replaced Ellis to make his 50th European Cup appearance, revealed that England skipper Corry never gave up the ghost.
"With 90 seconds to go, Cozza said we could still win, but even I doubted it," said Healey.
"We never gave up, and that is what playing for Leicester is all about."
The Ospreys are now out of quarter-final contention, and the defeat will be a bitter pill for coach Lyn Jones and his players to swallow.
"We missed 20 points from the boot today, and Leicester have always had an ability to score from 100 yards, which they proved at the end," said Jones.
"You can only imagine our sense of devastation - it is difficult to stomach at present. We looked the better side for about 83-and-a-half minutes of the game."
Try-scoring skipper Barry Williams added: "We had our chances, but we missed a lot of kicks and we have only got ourselves to blame.
"It will take a few days to get over this result, and it was like a morgue in the dressing room afterwards."