Maybe you aren’t ready to try and block that person out of your mind yet if you are still “dreaming” about them.
The only thing I can really think of to try and keep someone out of your mind, temporarily, is try to occupy yourself with different people and revolve yourself around them. Go out and do things, and keep your mind on else where.
Maybe even occupy yourself with projects, hobbies, even chores around the house.
And try to avoid things that may remind you of that person.
But I honestly don’t think you’ll be able to permanently get this person out of your mind. Maybe for a couple hours, at best.