Drupal 7 views: Get NID in views using contextual filters
If you are loading and displaying your view in the node.tpl or node--&lt;content-type&gt;.tpl file, you could supply the current node nid as an argument to your block view, then you can setup a contextual filter for Content: Nid. I would do something like this:

// get view
$view = views_get_view('YOUR_VIEW_NAME');
// set display for view
$view-&gt;set_display('YOUR_VIEW_BLOCK_NAME');
// set current node nid as argument to view
$view-&gt;set_arguments(array($node-&gt;nid));
// execute view
$view-&gt;execute();
// render view
print $view-&gt;render();