Remove blocked friend request in Facebook?

This solution if valid if someone else made the request to you. If you made the request to someone else and he blocked you, you can not do much about it. Maybe sending him a message to unblock you would help.
If you deleted the request then you can do nothing about it. If you pressed "Not now" you can find it by clicking on the "Friends Request" image on the top right of the page (next to the facebook logo) and then click on "See all friend requests". Then click on "see hidden requests" if you can not see the request you are looking for. Find the request you want to accept and click on "Confirm".