Schjelderup, 21, who last year played for Danish side FC Nordsjaelland, told the Copenhagen court he had received the 27-second video on the Snapchat social media app and had forwarded it to a group chat of four friends.
The winger, who now plays for Portuguese club Benfica, on Wednesday pleaded guilty and told the court he had realised from the first few seconds that the people in the video were under 18.
"As I forwarded it to my friends, I quickly realised that it was illegal and rapidly deleted the video," Schjelderup said.
In a statement on Instagram on Saturday, Schjelderup apologised and said he wanted to "be open to all of you about a stupid mistake I did".
Judge Mathias Eike gave Schjelderup a two-week suspended prison sentence, meaning he will only have to serve time in jail if found guilty of another crime during the next 12 months.
The prosecutor in the case had asked the court to sentence Schjelderup to at least 20 days in prison.
His lawyer, Anders Nemeth, told the court that the defence would take time to deliberate before deciding whether to appeal.
Norway on Sunday qualified for the 2026 World Cup after a 4-1 win away to Italy in their final qualifying match. Schjelderup was an unused substitute for the match in Milan.