How to limit direct access to URLs of nodes that are shown in a video gallery created with Views? I have made a video gallery using Views. But I only want that the page accessible to public and prevent access to each of the videos individually.

The videos had to be created as a type of content, so all of them have accessible ULRs like /content/video-1, etc.
Try content access module and prevent access to video content individually( or also you can set access to it for you desire roles )


  This module allows you to manage permissions for content types by role
  and author. It allows you to specifiy custom view, edit and delete
  permissions for each content type. Optionally you can enable per
  content access settings, so you can customize the access for each
  content node.


Also you can use Node View Permissions module, but I suggest use Content access module.   

(if you want work with drupal for future is better getting involve with this useful modules)