As discussed in http://law.stackexchange.com/questions/3446/sexting-and-age/, in NSW there are a number of defences, the most relevant being:

 - Innocent possession:the defendant did not know, and could not reasonably be expected to have known, that he or she possessed ...
 - Approved research: was necessary for or of assistance in conducting scientific, medical or educational research that has been approved by the Attorney General in writing ...

From the circumstances, you could avail yourself of the first defence. If you had sought prior approval (which you haven't) then the second would be open to you.