It comes after a schoolgirl who sent a topless picture of herself to her boyfriend received a police caution.
Her boyfriend also received the same penalty after he showed the image to his friends following an argument.
Nottinghamshire Police said the pair committed the offence of 'distributing an indecent image of a child' because both were under 18.
The two teenagers' exact ages were not released by police.
In a separate case, a boy who took a nude picture and sent it to friends as a joke also received a caution.
A caution is not a conviction but does mean the person will have a criminal record.
It could even mean the girl and boy involved being placed on the Sex Offenders' Register, although an officer told Radio Five Live that this was unlikely.
The force has written to every school in the county advising them to warn pupils.
Det Sgt Jan Rusdale said: "When they come to getting a job this would then count against them.
"We just want to get the message out there that this is a very serious offence."
Sean Kelly, head of Nottingham's Top Valley Academy, said: "We try to make students realise the danger they put themselves in if they engage in this kind of activity."
ChildLine received 351 calls about sexting last year, a 28 per cent increase on a year earlier. Most came from 12- to 15-year-olds and nine out of ten callers were girls.
More on Parentdish: The dangers of teenage sexting