Pakistan and India have been hostile since they first were separated from each other, but they're not so different!!
The people of Pakistan and the people of India have been hostile toward each other much longer than that. Of course, they weren't "people of Pakistan and India" before the end of British rule of what is now India and Pakistan.
About the only period they weren't hostile was during the Raj, when the British tried to prevent that sort of thing.
Note that during the post-British period, when they were split into two countries, the Hindus living in what is now Pakistan were attacked by their Muslim neighbors and driven out of the country.
Likewise, during the same period, the Muslims living in what is now India were attacked by their Hindu neighbors. This reached the point that trainloads of Muslims fleeing to Pakistan were stopped by the Indian Army and machinegunned before being allowed to continue into Pakistan.
Surely this gesture will make them realize this and they'll have no choice but to bury the hatchet, that's just how human psychology works.
Bury the hatchet in each other's head, yes.
The way you mean it, no.
And do you really know so little of human psychology?