Screen turned into purple screen

Jawahar, assuming you've tried the software solutions such as resetting your phone, power off/on, etc., then the most likely issue is the screen has failed and would need to be replaced. On your phone it isn't too difficult; here's a video showing you how.

how to samsung galaxy j2 broken lcd replacement - YouTube

The one issue I have with this video is that they did not take the time to clean the old adhesive off the phone before installing the new screen; that will cause problems when the old adhesive starts to fail. But otherwise you can try opening up the port in the back where the display connector lives and try reseating it; unplug it then plug it back in just in case it got knocked loose or something.

If that doesn't help then I'd suggest going ahead with a screen replacement; as shown in the video you can easily test a new screen before you even take the old one off to ensure it will fix the problem. You can find replacement screens on various sites such as Amazon, eBay and AliExpress among others.