It is incumbent on the one performing Hajj Mutamatu’ to pay the ransom and slaughter animal during the time of Hajj in Mínà. It is not right for him to postpone it till he returns to his country.
If he’s incapable of buying what he his redeemed, it is imperative for him to fast for three days during hajj and seven after returning to his country. For Allah says:
“… then whoever performs ‘umrah [during the Hajj months] followed by Hajj [offers] what can be obtained with ease of sacrificial animals. And whoever cannot find [or afford such an animal] – then a fast of three days during Hajj and of seven when you have returned [home]. Those are ten complete [days].” [Quran 2 : 196 ]