@niteshverma what you are describing actually sounds like a damaged screen. We would need to know what this looks like. Post some pictures of what your screen shows with your Question. Again, what you are describing sounds like a bad screen. If that is the case, you will need to replace it. [guide|21499]
Since iFixit does not yet have a specific guide for that use something like [https://www.youtube.com/watch?v=T81pGnXIwgg|this video] Replacement screens are readily available at many online stores
While you work on your phone, take lots of pictures. Once you are done with it, take those pictures and create a guide for iFixit. That will help the next person that has a device with the same issues as you do. It's easy and fun to create these guides. https://ifixit.com/Guide/new The iFixit community will appreciate this.
Repair is War on Entropy!