Thanks for joining Apple Support Communities, khwajababu.
I use Apple Maps frequently myself. When I'm trying to find a location in a large city, I'd rather hear the direction then need to keep referring to my iPhone. So, since Maps is available in India and you're on the latest iOS version, let's see if I can get to the bottom of this. Feel free to skip any steps you've already tried. After each step, see if that's fixed your Maps App.
Here are the basic troubleshooting steps you should try.
Get help with Maps
If you've already completed those steps, I want to urge you to make a fresh backup of your iPhone 6s.
How to back up your iPhone, iPad, and iPod touch
Since the Maps App is part of the iOS, that would indicate there was a problem with the installation on your iPhone. You'll need to use iTunes to completely clear off the phone's hard drive and install a new copy. Using Settings on your iPhone will only remove your personal information.
Use iTunes on your Mac or PC to restore your iPhone, iPad, or iPod to factory settings
The first time through, when the Setup Wizard asks you what you want to use to set up your phone again, select "Set up as new iPhone". Enter your Apple ID for iTunes & App Store and iCloud, turn on Location Services by tapping Settings > Privacy and make sure your iPhone is connected to the internet through either Settings > Cellular or Settings > Wi-Fi, then see if Maps is working as it's supposed to. If it is, you can restore your information to your iPhone.
Restore your iPhone, iPad, or iPod touch from a backup
Happy travels!