[Assentesy]

Today my son attempts to chip his ball onto the green but strikes my ball with his in the process. My ball was on the fringe at this time but was bumped onto the green after the collision. I looked at him an said, "Not sure what the rule is for this". We played as they lie after the collision. I've never run into this before so curious to the correct ruling. I did a quick search on ask.com and it says that I should have received a 2 stroke penalty for what I did. It says to put the ball back where it was and there is no penalty but I couldn't put it exactly where it was. Do I just drop the ball back in the vicinity of where it was to keep from the 2 stroke penalty?