Green Line appears on screen after display on?

[aha18]

The Green line doesn't show up if I switch off the phone and on it. But when you use it for a while and put it on screen lock mode display off) and switch it on back after a while (about in 10-20 mins) then a green color line appears and it's very clearly visible on grey colors. And later on another mildly visible line appears right below the top line on the bottom side but it's not as visible as the line appears on top. Is it display problem? do i have to change the display?

 

[webworkings]

It sounds like your display is starting to go. So, yes I would consider replacing it (if is an expensive phone that is) before it fully goes and gives you no access to the device.

Also, I would really suggest you back up all your files, photos, videos, music, contacts, etc., to a computer or cloud account now, rather than later. Why? Well once that screen goes, you may not be able to get all that stuff. Granted it may not go before you can replace it, but better safe than sorry.