David Luiz’s 38th-minute penalty put Chelsea ahead in their crucial Champions League clash after both teams had missed from the spot.
And Fernando Torres ended his latest goal drought by doubling the lead just before the interval.
But Chelsea will become the first holders to exit the tournament at the group stage unless they win tonight and Shakhtar Donetsk beat Juventus.
The game in Ukraine is currently goalless, meaning that as things stand the Blues are going out.
Nordsjaelland, forced into an early change when centre-back Ivan Runje was stretchered off, spent most of the opening 45 minutes on the back foot.
Their keeper Jesper Hansen produced saves to deny Victor Moses, Luiz and Eden Hazard.
Skipper Nicolai Stokholm then sliced Moses’ low cross onto his own crossbar as the visitors rode their luck.
Yet they were given a golden chance to go ahead when Gary Cahill was harshly adjudged to have handled the ball inside the box.
Cech dived to his right to keep out Stokholm’s kick and two minutes later Chelsea were given a penalty after Cahill’s header hit the arm of Mikkel Beckmann.
Hazard failed to convert from 12 yards, his tame effort being easily saved by Hansen.
But Luiz made no mistake with the game’s third penalty, which was awarded after Juan Mata’s shot had cannoned into the hands of Joshua John.
And after being set up by Moses, Torres side-footed home the rebound after his first effort had been saved by Hansen.
Chelsea: Cech, Ivanovic, Luiz, Cahill, Cole, Romeu, Ramires,Hazard, Mata, Moses, Torres. Subs: Turnbull, Oscar, Mikel, Ferreira, Marin, Azpilicueta, Bertrand.