https://en.wikipedia.org/wiki/Hindi-Urdu_kinship_terms

बुआ is just another way of saying फूफी, they are both a father's sister.

Hindi seems to be much more specific about how two people are related. This link does a pretty good job of explaining when you use each different word for "aunt", "uncle", "cousin", etc.

https://www.omniglot.com/language/kinship/hindi.htm

I put his father and it was accepted