Anyway to redirect to previous URL after registration in Joomla

In your component you could try to store the referrer in the Joomla! session - I don't believe the session changes or is replaced during login. I haven't had time to try this but it should work.

To Save:

$session = JFactory::getSession();
$session->set('theReferrer', $_SERVER['HTTP_REFERER'], 'mycomponentname');
To Retrieve:

$session = JFactory::getSession();
$redirectTo = $session->get('theReferrer', '', 'mycomponentname');
Then you can just use a setRedirect before you return.

$this->setRedirect($redirectTo);