Indigo does not interline baggage on separate tickets.

They offer discounted excess baggage pre-booking for international connecting flights within 48 hours: https://www.goindigo.in/add-on-servi...baggage_header

Another possible solution might be for you to try the "double seat" option on Indigo which will give you 10kg excess baggage for possibly a lesser fare than the excess baggage: https://www.goindigo.in/information/6e-double-seat.html

In general for domestic-international transfers with baggage it is recommended to book on a single ticket to avoid these issues.