Judge Michael Crosbie told Nuku in his judgement he was aware some in the community would "throw the book at you'' if they had the chance, but he had to be even-handed and take note of other court rulings.
That was despite a probation report that said Nuku had failed to face up and take responsibility for what he had done.
Nuku had pleaded guilty to the crime, and another charge of possessing on his mobile phone a text document entitled Daddy's Little Girl, a story about a sexual relationship between a seven-year-old daughter and her father.
He was sentenced to six weeks in prison for that offence, to be served concurrently.
The offences occurred in April last year in Palmerston, and the victim was transported by ambulance to Dunedin Hospital on April 10.
The child's mother, Honey Samson, said outside the court the victim impact statement she tearfully delivered to the court could not get across the depth of the hurt that had been caused by Nuku.
She was "absolutely shocked'' at how short the sentence handed down was, but said there was nothing she could do.