The African champions dominated much of this match and had enough chances to win a few games, but their profligacy in front of goal - which had already been in evidence in their 1-0 defeat to Korea DPR - once again proved their undoing.
Germany, meanwhile, were indebted as much to Nadine Angerer as they were to Stegemann, their unlikely goalscorer, with the ever-impressive keeper coming to the rescue of last year's FIFA Women's World Cup winners on more than occasion. She was certainly needed to keep the Nigerians at bay in the first half as the Africans pegged the European and world champions back in their own half.
This pattern of dominance continued into the second half, with Sarah Michael passing up a glorious opportunity to score in the 55th minute and Perpetua Nwocha also going close.
The Germans, however, are past masters at grinding out results and, for all that their overall play remained hugely disappointing, their reputation ensured that there was no great surprise when they opened the scoring against the run of play. Substitute Anja Mittag was the goal's architect, racing forward on the left before delivering a precise low cross that Stegemann, lurking at the far post, had little trouble in diverting home from all of three metres.
The goal sealed a win that leaves Germany top of Group F, for a couple of hours at least, on four points, with Korea DPR - on three points - set to play Brazil, who have one, in the day's later kick-off.