You cannot unblock your account once Facebook has blocked it due to sending too many friend requests. You will have to wait until the given time lapses before FB unblocks you automatically. Once the block has been lifted, send requests over a period of time rather than all at once.
normally fb requires the user to answer security question/identify friend's photos. if that is only reason you got blocked it should unlock. but if someone reported your profile; that might be harder because fb handles issues by their policies. good luck.