The Gunners had appeared set for a frustrating start to the new year as the Bluebirds, with potential new boss Ole Gunnar Solskjaer watching from the stands, battled towards what would have been a much needed point in the face of sustained pressure from the home side.
However, with just two minutes left, substitute Bendtner crashed the ball in from close range after David Marshall had saved Bacary Sagna's header. Then, in stoppage time, Theo Walcott sealed a victory which took the Gunners back above Manchester City.
Bendtner is now set for a spell on the sidelines having sprained his ankle as he put the ball past the goalkeeper.
However, Wenger will wait to decide how he tackles the January sales, with the squad in need of some attacking reinforcements as lead frontman Olivier Giroud is also troubled by his own ankle problem.
"I don't know, it doesn't mean we go straight from Nicklas' ankle straight to the transfer market," Wenger said.
Wenger believes Bendtner's goal was reward for his positive attitude since returning to the first-team picture this season.
"Nicklas is a player who has gone through some difficult periods, so I just want to give him great credit," said Wenger.
"I told him already that he is back to the level I want him to be at, and if he continues to develop like that he will come back into the team.
"Unfortunately he got injured and it looks like it is not a question of days, but weeks.
"He was a bit unlucky. He said he landed on the foot of a Cardiff player and sprained his ankle."