how to put in if clause ?

i use this code to echo thumbnail for first post in loop.

[ Moderator Note: Code backticks fixed. ]

<?php $count = 0; $loop_baihoccuocsong1 = new WP_Query('cat=3&showposts=1'); // Them category 2
while($loop_baihoccuocsong1->have_posts()) : $loop_baihoccuocsong1->the_post(); ?>

    <a>" rel="bookmark" title="<?php the_title_attribute(); ?>">
        <?php
            if($counter==0)
                {
                echo '<img src="<?php echo get_post_meta($post->ID, "thumbnail", true);?>;$counter++;"/>' ;
                }
        ?>
    </a>

    <div class="h_bai-hoc-cuoc-song-1">
        <a>" rel="bookmark" title="<?php the_title_attribute(); ?>"><?php the_title(); ?></a>
        <?php the_content(); ?>
    </div>

<?php endwhile; ?>
<?php wp_reset_postdata(); // Reset the query ?>

There are any error in if clause.
Browser cannot echo url thumbnail.
Please help me fix it.
Thank you !