It sounds like you already created a child theme? If so, just copy the header.php from the parent theme’s folder to your child theme’s folder.
Find this code in the header.php file:
<div class="header-image">
<?php $header_image = get_header_image();
if ( ! empty( $header_image ) ) { ?>
<a href="<?php echo esc_url( home_url( '/' ) ); ?>" title="<?php echo esc_attr( get_bloginfo( 'name', 'display' ) ); ?>" rel="home">
<img src="<?php header_image(); ?>" width="<?php echo get_custom_header()->width; ?>" height="<?php echo get_custom_header()->height; ?>" alt="" />
</a>
<?php } // if ( ! empty( $header_image ) ) ?>
</div>
and replace it with:
<div class="header-image">
<?php
if (is_front_page()) {
$header_image = get_header_image();
if ( ! empty( $header_image ) ) {
?>
<a href="<?php echo esc_url( home_url( '/' ) ); ?>" title="<?php echo esc_attr( get_bloginfo( 'name', 'display' ) ); ?>" rel="home">
<img src="<?php header_image(); ?>" width="<?php echo get_custom_header()->width; ?>" height="<?php echo get_custom_header()->height; ?>" alt="" />
</a>
<?php
}
}
?>
</div>
You don’t need to worry about the get_header() function. It’s not involved with the header image.