Who is Wrong - Traffif one of the situation

Driving in the other side of road at 11:55 PM night. An Truck is also moving in the same direction (Night we can go in wrong side too, if I am not wrong). The truck slightly hit the bike and bikes side signal light was broken. What you do if you are in that situation? How to handle traffic hazards/accidents and convince the affected? Did you face any and handled any accidents? What are traffic rules in your place?