Load current node from block and from display suite field
You can load the node id from node page using arg function...


  Returns a component of the current Drupal path.
  
  When viewing a page at the path "admin/structure/types", for example,
  arg(0) returns "admin", arg(1) returns "structure", and arg(2) returns
  "types".


node pages always has path 'node/nid' so arg(1) gives node id...

$nid = arg(1);
$node = node_load($nid);