This is a hardware issue with the screen. Have the screen replaced. Even if the top glass you can see isn’t broken, the actual display underneath can be damaged.

Hardware issue, replace the screen

thank you! is it a serious problem that needs to be fixed immediately?

thank you!

No, if you can deal with the weirdness, then keep using it. It isn’t damaging thing and you could replace the display at any time and it will be fine.

thank you very much!