It IS ok to pull your foreskin back. That's what it's meant to do so that you can wash underneath it. If you mean is it ok to pull it back and leave it back, then yes that's fine too. Many men do that for various reasons (cultural, aesthetic, cleanliness) but it might take some practice to get it to stay back at first. If it gets sore you might want to cover it up for a while but in general keeping your foreskin pulled back won't do you any harm as long as it isn't painful.
