My iphone7 is US purchase. Does the warranty covers in India for screen damage repairs??

No. Warranties for phones have to be serviced in the country of purchase. You will need to ask at a service centre for prices. Be prepared; there are no fixed prices as such, in India. All stores there are privately owned and it has been reported that they charge as they see fit.

One last point. If you have a friend in the USA and can send it to them to get repaired, be sure to send a letter that includes a copy of the receipt and authority to speak on your behalf.