Lloris required medical attention after being caught in the head by Lukaku's trailing leg in the second half, and Villas-Boas admitted after the final whistle that the Spurs goalkeeper still did not remember the moment of impact.
The doctors were keen to take Lloris off and Brad Friedel prepared to come on, but the Frenchman's desire to continue convinced Villas-Boas.
"The medical department was giving me signs that the player couldn't carry on, because he couldn't remember where he was," Villas-Boas told Sky Sports.
"That is the situation right now - he doesn't remember the impact.
"But he was quite focused and determined to continue, so when you see this kind of assertiveness it means he is able to carry on, and that is why it was my call to delay the substitution.
"You have to make a decision in situations like this but from my knowledge of Hugo he seemed okay to continue.
"It was a dreadful situation. You can imagine the impact of a knee going against a goalkeeper's head.
"It happened unfortunately to Petr (Cech) so it is good that the players immediately went to him and it is very fortunate that it was nothing serious."
Both sides had penalty appeals following incidents involving Jan Vertonghen and Seamus Coleman, but Villas-Boas felt referee Kevin Friend had a 'very good game'.
And the Spurs manager was satisfied with a point after an evenly-contested encounter at Goodison Park.
"We had a very good first half but Everton put in a big effort in the last 30 minutes," he said.
"I think we had the better opportunities but I would say it is a fair result and for us a good point.
"We wanted to put them under real pressure. We just could not make the most of the mistakes we forced but it was still a great performance from the team."