mysql_fetch_array, does what it says fetches an array, you are trying to do a string compare on an array you probably want something like $value['password']
if(!(strcmp($value['password'],md5($pass))))
{
echo "Willkommen, " . $nickName;
}
else
{
echo "Passwoerter stimmen nicht ueberein!";
}
and of course think about using mysqli as mysql is deprecated