Nested conditionals

If I understood you correctly:

<?php
//if home, do nothing
if( ! is_home() || ! front_page() ) {

    //if has post thumbnail
    if( has_post_thumbnail() ) {        
        the_post_thumbnail( 'full' );
        echo '<h1 class="entry-title">'. get_the_title() .'</h1>';
    } else {        
        //no post thumbnail, show normal entry title
        echo '<h1 class="entry-title">'. get_the_title() .'</h1>';
    }

}

or, it can be done easily:

<?php
if( ! is_home() || ! is_front_page() ) {

    if( has_post_thumbnail() )
        the_post_thumbnail( 'full' );
    echo '<h1 class="entry-title">'. get_the_title() .'</h1>';

}