I got hit in the chest with a glider I was trying to catch. Hurt like heck, but it was my fault. I have always been very careful not to put myself or anyone else close to my prop. Only make sense. No mater how good a flier you are, things happen! I hope your son is OK. I'm sure you feel like poo-poo, and I hope you have learned to respect what an engine can do, and fly safely!