Hi shankar. Keep in mind that damages due to misuse, abuse, or accident are not covered by warranty. In your case, I suggest that you take it back to the store where you bought it.

It seems like many are starting to raise complaints who own the new Samsung Galaxy J7 (#GalaxyJ7). This problem is characterized by a blank screen that is often unresponsive in a sense that the phone won’t respond when you touch it. There are cases wherein the device is powered on even if the screen is dead that’s why some owners reported they continue to receive text messages and emails or even phone calls even if the screen is all black.

There are several possibilities that we have to consider when troubleshooting an issue like this. Of course, there’s the possibility of a minor app or firmware issue and there is another possibility that the problem is due to water or physical damage. So, we really need to troubleshoot the device thoroughly to determine the cause and what needs to be done to fix it. 
Get Some help Here