If the problem is that you have two colliding objects each incrementing the score in their collision callback when you only want one of them to, you need a way to decide which of them is going to do it. I have that issue in my bowling games when a pin is colliding with another pin and I want only one of them to play the pin collision sound. In that case, I check the gameobject unique IDs and decide that the lower number gets to play the sound. Sample code here.