Is it ok to like someone you don't know and ..?

Taking your question I will try to put it into prospective for you. As a guy or a female liking someone else we all have to start first with some interest with the opposite sex. I would advise you first to make contact with him in a general way that leaves him wide open to possibilities of his interest in you or lack of interest. He is looming out there not aware of you and you need to make that first contact. Observation, simple comments (mostly meaningless but set on speaking to him, to see if that arouses some kind of response) Guys stare, look around, observe and ponder at certain girls or women trying to wonder if that might be a chance to meet them. Girls do the same. They do with more subtly and less noticeable to the guys. Guys tend to be oblivious of girls liking one guy or another unless someone else points it out. They might know because they were told by her. Guys walk around with blinders. Communication is not their strong suit. Complaints on texting or phone calls by complaints by females can attest to that point. Guys need to be told eventually, but first you can work up to it, if you want to be cautious and might be a little shy yourself. Take your time, as guys move so slowly anyone you have a life time to practice. lol......

He may be a bit shocked and confused. You would be putting him in an awkward position, as he's not going to ask you out if he knows nothing about you. It's fine to like him, but I think you should try to get to know him before telling him.