Minor accident

I got involved in a minor accident a month back. We were driving our car and by mistake while crossing road a speeding motor bike hit us and he fell down. There was a old lady in the bike who was injured as well. We then took them to hospital and in hospital doctor said it was just minor injuries and not so serious and treated them. We also paid the necessary compensation for that, however they made us to write a letter stating the same. we wrote that we paid so much amount and settled, and if in case there are any further problem they can reach us . We just wanted to leave the scene as there were too many people in the place. Now after a month they are calling and asking for more money stating that there is more to pay or they ll file a case. I asked them to go a head with filling a case and we ll deal if they file and I blocked the number.they tried reaching from different number but I didn't pick the call. Kindly let me know on actions to be taken from our side.Questions from my side are 1.Should I have to take some precautionary steps like take bail in advance and will I be able to?? 2.I felt that I have no other choice to face this legally. is this the right way now? 3.will they be able file and proceed a case in this matter? Some other details : my vehicle is a TN registration and the accident happened somewhere in Karnataka close to Mysore road