you need a while(){


like you have:
$query=mysql_query("SELECT id FROM comments WHERE nid='$id'");
$totcomms=mysql_num_rows($query);

do
$query=mysql_query("SELECT * FROM comments");
$totcomms=mysql_num_rows($query);

while($row=mysql_fetch_array($query)){
$query2=mysql_query("SELECT * FROM comments WHERE nid='$row[id]'");
$totcomms=mysql_num_rows($query2);
echo"$totcomms";


}