The Wales star had to be helped from the field by two members of the medical staff, but he somehow managed to come back on and complete the game.
Not only that, Biggar made a vital tap tackle on Jasper Wiese late on to help Saints secure a crucial 23-18 Gallagher Premiership win against local rivals Leicester.
And when asked about his 74th-minute collision with Nemani Nadolo, which appeared to cause an injury, Biggar said: "He's definitely got the better of me, no doubt about that!
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"But it was just a scare more than anything and I managed to dig in as much as possible because we were down to 14 (JJ Tonks was yellow carded) and really up against it."
Biggar was deservedly named man of the match after keeping fifth-placed Saints in the hunt for a Premiership play-off place.
And he added: "The character is unbelievable.
"To be fair to Leicester, I thought they played really well in that second half. They had a couple of cards but they kept coming in wave after wave after wave.
"But fair play to the lads because we just dug in.
"There were some really key turnovers.
"We played some horrible rugby in that second half - it was so, so bad, honestly - but we managed to grind it out.
"It's maybe a bit harsh to say it was horrible rugby, maybe we should have kept the ball a bit better and that was a frustration for us and our discipline just hasn't been good enough in the past couple of games.
"But we spoke about stepping up and physically fronting up - and to a man we managed to do that.
"When we moved the ball and moved the point of contact, that's what our game is but when we tried to get into a Leicester type game with them is when we came off second best.
"I'm just really relieved and it was really important, especially with the other results with Sale and Harlequins winning.
"It was really important for us."