Being blackmailed for a road accident

Hi, Almost a week ago, on our way back home, we met with an accident. Our car hit a small girl who aimlessly ran across the road (main road). I am not even sure what the girl was upto because he appeared quite suddenly. My husband applied the brakes immediately but being on a speed of 40 , the car didnt exactly stop instantly and the car hit the small girl. Shocked beyond belief, we got out to see what exactly happened. The girl luckily was alive, but was bleeding from her leg. People gathered around and they asked us to leave as they told us it isn't our fault and the girl ran in. For a humanitarian cause, he wanted to help the kid.. so we asked the people around there about her parents. Her mother was on the other side of the road and came running making a scene that we killed her daughter (the girl was alive and crying!) We took the kid and her mother to the nearest hospital . The girl has a fracture in her leg (bone displacement) and we were advised to take her to a bigger hospital or a bone setting centre. We chose to take her to a reputed hospital in order to ensure best treatment for the kid. The hospital told us that there would be surgery needed and we needed to file a HLC. We even agreed to pay the cost of the surgery (which was coming close to 90k). Meanwhile, the family of the girl comes .. and were surprisingly very co-operative (they looked very rowdy). They didn't trust private hospitals and wanted to get her discharged as they wanted her to be treated by a known doctor in their village. As it is the parents consent, we agreed to it and even paid the family 30k (they looked poor and we wanted the best for our kid). The family got the kid discharged, and we went back home. For the past 3 days.. we've been getting calls from that family at very odd hours, with the mother of the kid literally blackmailing us that she'll put a legal case against us if we don't pay her more money. She is demanding 50K more. My husband is willing to do that in order to settle this matter. But I am very sure they'll keep asking us for money again.We are very unsure on what do to. Is there any way where we can use the law to settle this matter officially? This is wrt the fact that the girl ran across the car and we did the most we could do that moment. Local people near the accident site even asked us to leave as it wasn't our fault. Is there anything we can do to stop them blackmailing and preventing them from asking us money going forward ?