I don't think there is any doubting the bitter animosity between India and Pakistan. They truly to hate each other's guts.
But the fact that both of them have nukes may keep the lid on this thing. They both know that even if they launch first, they're likely to lose one of their major cities before it's over. That's beyond suffering the international fallout from use of nukes.
They may scream and shout a lot, but I don't think either side is willing to launch the first nuke.