Warranty for iPhone and everything else in the box is valid
only in country of original purchase. You can take your iPhone
and earpods to Apple in India, but don't be surprised if they
refuse to assist as the iPhone is not from India.
Did you check Settings=>General=>Accessibility and scroll
down on the Accessibility page to the setting where you can
adjust speaker division between left and right - it may have
right side turned off.
Did you test earpods in another iDevice? Did you test another
headset in your iPhone? Are the earpods pushed all the way in?