India has the most clearest of nuclear doctrines as far as the nuclear weapon states are concerned, India has clearly stated that it will not be the one to initiate a nuclear conflict be it China or Pakistan or any other nation as it's adversary, but the response to a nuclear attack will be massive & unaffordable for the attacking nation. Not just a first nuclear attack but even chemical or biological attack would demand a nuclear response from India. Now when u state this policy there is no such thing as small nuclear attack or larger one, the question is that Indian people/armed forces are attacked with a (tactical) nuclear weapon, this opens the possibility of any type of attack from India (a murder is a murder, it's not about nos., u cannot give smaller punishment for a single murderer & larger punishment for more than single murder), the world will also not object to this as they know that India was at the receiving end & is just retaliating, so IMHO using a tactical nuclear weapon on Indian armed forces will be as dangerous for Pakistan as using strategic weapons.