Most Helpful Guy
A person usually receives a notification if someone likes their post. If they were online when you liked that post, they might have seen it. If they had a lot of notifications, they might not have seen it. Unliking and blocking should have been enough. If you block someone, they won't even be able to find your profile or comments on pages. To that person it's like you don't even have a Facebook account.
Most Helpful Girl
If the person was online right as you liked it, then he or she might have seen it. I wouldn't worry about it so much, though.