child found mom's nudes

I'm babysitting and the youngest child (5) had his mom's old phone. He said she gave it to him because she got a new phone. He took a picture of me with the phone then went to look at it and saw there were inappropriate pics of his mother's body. I got him playing with something else now but what do I do? it did not have her face in them so I don't think he knows it was her. What do I do?