Since version 1.1.0, Nirvana includes support for WooCommerce and the compatibility child theme is no longer needed. If you’re still using an older version we strongly recommend to update (or you can still try the compatibility child theme).
WooCommerce sections will use the configured layout (sidebar placement) by default. You can override the behaviour of individual pages (Checkout, Cart, Account) by defining a specific layout page template on that page.
For sections that are not pages but which you wish to disable the sidebar on, the theme provides two woocommerce files. Delete (rename) the initial woocommerce.php (which features sidebars) and rename woocommerce-nosidebar.php to woocommerce.php to disable the sidebar on WooCommerce sections that don’t use a layout page template.