Saw something on my FIL’s phone I wish I hadn’t

Recently my not so tech savvy FIL was having issues with his iPhone after a new software update, so I was happy to help him out. To get around the software update issue I had to log into his iCloud account on a laptop and when I did, his photo library popped up and I saw two pics of his BIL’s partner in a bikini on a big group family holiday we had all been on a couple of years prior. The pics looked like they had been taken in a covert manner and as soon as I saw them I felt a bit sick, suspecting that there was some seedy intent here. I quickly scrolled away so my wife wouldn’t see them too, did what I had to do to fix the phone and closed the browser. But having seen these images and knowing that he’s still in possession of them, I find myself in a real moral quandary. I feel like this is one of those things I’ll just have to try and forget about and never tell anyone? I don’t really want to tell my wife about this, as her and her dad have a good relationship and I don’t want to affect that. But I don’t think it’s my place to raise it in private with the FIL either. Any outside perspectives on this appreciated.