I've got a white dotted line on my HP Envy

[Fatima123]

Yesterday, a white line appeared on my laptop screen. It's vertical and on the extreme right of my screen. It doesn't look like the screen was damaged or anything. This happened after my sister was messing around with the laptop. How do I make it go away?

 

[Fatima123]

Update: Another line is appearing on the centre of the screen. It blinks, stays for a while and then goes away.