@rishi22 I assume you are talking about the display. Most likely a screen issue. I would get ready to replace it. While you are working on it, make sure that all the ribbon cables are properly connected and that there is no corrosion etc. in any of the connectors. Use something like [https://www.youtube.com/watch?v=z3GjTQ0KN78|this video] to work on your phone and to replace the LCD. Replacement displays can be found at plenty of places with an online search.