The Space Liability Convention of the Outer Space Treaty holds that whichever state controls the territory a spacecraft/object is launched from is responsible for any damages it causes.
India is a signatory of the treaty, so if the debris field results in damage to the ISS, the appropriate states (depending on what specifically was damaged) can file for compensation from India.
The only example of this in action was in 1978 when the Soviet Union lost control of a nuclear powered satellite which then deorbited and spread debris over Northwestern Canada, some of which was radioactive. The Soviets paid roughly $3,000,000 to compensate for the cleanup efforts.
Edit: Adding some clarification to better address the question.
While the Space Liability Convention doesn't differentiate damage caused by actions of a military context, it's a reasonable assumption that there could be ramifications separate from the treaty. For example, demonstrating the ability to destroy satellites might be perceived as provocation or aggression by another state, who might then respond more harshly to any damages it caused them (from sanctions to outright military action, hypothetically). But in the specific case of India, I think it's unlikely; They seem to be on friendly enough terms with the main players in space.