Well, here's another way to look at it....how do you know he hasn't watched the same videos? Just a little advice, if it's something that you will be ashamed of if someone finds out about it, don't do it!
I actually watched some porn videos on YouTube and my friend borrowed my laptop. He went through all the history and he got to know that I watch such videos. I feel so ashamed now to even talk to him?
Well you both did two things wrong: one you shouldn't be watching stuff like that and two he was wrong for going through your history. So I don't know what to say, you can either talk to him about it or leave it as it is.. he will eventually get over it.
Don't feel ashamed. But let him come talk to you so you know he didn't find it weird. I don't mean you should block him out until he finally gets the guts to talk to you. Just say hi, hey, bye, see ya later occasionally if you feel like it. Plus why should you be ashamed if he watched through your history? That means he may have watched the videos too.