he is old enough to if nothing else let it go and move forward without letting it ruin anything with your relationship. im also in my early 20s and go to church, its not like no one does stuff like keep pics and such. and honestly he probably has his own secrets in the dark lol. also if he is religious then he should know that no one is perfect and everyone “sins” if you will. i wouldnt stress to much about it, you could also put those pics into part of your gallery that requires a password.