By admitting he sent the nude photo he is already a felon.

I would destroy the hard drive of the computer even though they can still trace the message back through an IP address but not having the original computer or the photo or the archives of where it was sent from might be a small benefit for him, but might also get him charged with obstruction of justice. Of course I’d rather fight obstruction charges any day over child porn charges, and obstruction charges don’t require having to register the rest of your life.