I has with my friends dad, And don't know if i should tell him or not? help!?

I am 19 years old male and gay. I have been friends with my friend saying no names,ill address him as Sam (not real name). I went round his house the other night, we're were watching a film, just him and me (he isnt gay btw we're just best mates) when his girlfriend called and needed picking up from the station, and because he lives in the countryside it was around 45mins away. He told me to stay at his while he went to go and get his gf, so i did. After he went i went into the toilet only to find his dad jerking off on the toilet. he jumped across the room, I apoliges and left quickly, as i was walking away, he called me back, so i went bad because otherwise i think it would of been rude? so i went back in, he some boxers on now, but then he came close to me locked the door and started to kiss my neck, i tried to push him away but he was pretty strong and confident, after a while before i new it he was sucking my Pe*is. I wont lie, i felt good, and so it lead to him sticking it in my A*se and ming inside me , then we switch and he was so tight and it felt so good. After would he told me to to tell 'Sam' and i havent but i dont know he i should, h has a right to know right? i feels so wrong now, but so nice at the time. Wat shall i do?