HP 19bii Problem with the screen

[math7]

Thank you very much Maximiliam for the links, you went to study them to dare to disarm my HP 19, because the truth I got it cheap at 10 dollars but I have seen others on the internet and it costs more than that, and the truth is that I got the keyboard and covers in very good condition, I think it's worth trying to repair that stain on the screen, and I hope the stain can be removed and not sea as the display ink