Rangers struggled in the first half but Dykes put them ahead just after coming on as a substitute midway through the second, and Yoann Barbet doubled the lead.
It was an emphatic return to action for the Scotland striker, who was recently laid low by illness.
Coventry failed to clear Chris Willock's ball into the box and Dom Ball intelligently headed back to Dykes, who fired into the bottom corner.
Warburton said: "Lyndon has been ill with a bug. He was hit particularly hard.
"He's come back and you saw his energy, the goal and his aerial threat.
"He was chomping at the bit to come on. He came off the bench, looked a threat, had a real presence and had the bit between his teeth.
"He made a real impact and he deserves a lot of credit today."
Rangers go into the international break unbeaten after five league games and second in the table, below west London neighbours Fulham.
But they rode their luck against a Coventry side who created a number of opportunities in the first half.
Goalkeeper Seny Dieng produced saves to deny Ian Maatsen, Callum O'Hare and Gustavo Hamer, with Martyn Waghorn also seeing an effort saved soon after the interval.
Warburton said: "It's fair to say we could have been one down easily. They were the better team in the first half. They were far more dangerous.
"We were second best in the first half and fortunate to come in at half-time with a clean sheet.
"We were much better in the second half but still nowhere near the level. To win that game, keep a clean sheet and get three points and not be at your best, the boys deserve enormous credit.
"The international break comes at a good time. Some of the boys are running on empty."
Coventry manager Mark Robins admitted the visitors paid the price for failing to take their chances when they were on top.
Robins said: "When you're in control like we were - against a really good team by the way - you need to take one of your chances and if you do that it puts a bit of doubt into them and the crowd.
"We have to take one of the chances we had early on to create that impetus."
Nevertheless, Robins believes the Sky Blues can take heart from their performance at the Kiyan Prince Foundation Stadium and their start to the season.
"It was a bit of a lesson for us, but there are lots of positives to take from it," he said.
"It's been a brilliant start to the season for us and with some rest and some work now, four of the next block of six games after the international break are at home, so there are some really tasty games there.
"We have to make sure that we get things right and not give up chances, but once we get into our stride I think we'll improve.
"The chances we're creating are really good chances so we have to be more ruthless, but we just need to be calm and go about our jobs in the way that we're capable of doing."