need advice -- found boyfriends nudes

So I was using my boyfriends comp last night and I had to send a photo attachment. When I went to the folder to select, I saw a bunch of dick and ass pics he had taken last summer -- when we were together -- but these pictures were never sent to me. This normally wouldn't be concerning, but my boyfriend and I have never exchanged nudes the entire 2 years we have been dating. He's really modest, and sometimes even hesistant about changing in front of me. I love and trust him completely -- and there's nothing that's happened that has suggested he has sent stuff to someone else -- but this just seemed so dramatically out of character both for him and our relationship that I feel strange. I know him so well and it was very surprising for me to see these photos of his boner, etc, when he is very conservative about that kind of stuff. Like, why would he take these extremely sexual photos, just for himself? That wouldn't be like him. I don't want to say anything to him because those photos are his private property, but it's eating away at me and I don't know what to do. Should I just try my hardest to forget I saw these, and let it go>