next time, send him in his cotton wool jacket with his bubble wrap trousers on.
Children love the freedom to run in the woods, they rarely stray too far, and amazingly they rarely get hurt! You send them to (cub) Scouts to do Scouty things - climbing, running, games, caving, kayaking, raft building, and burning things.
Relax.....all leaders are trained in risk assessment - plus we have the most monumental admin to do IF anyone gets hurt, which they rarely do! SO we do make sure that risk assessment has been carried out - we usually insist on being within earshot of leaders.
For example, I run Beavers.....(6-8 years) ....in the last 6 years, we have had 2 injuries, despite being a very active and outdoorsy colony. The injuries:
Child 1: Tripped on path, skinned knee, mum took him to A&E 
Child 2: Got something in his eye in the woods. Dad is a leader and everyone else had gone home safely! Eye flushed on site, but had scratched cornea. Dad was supervising at this point, as the rest of us were supervisng pack up. 
Relax and let him enjoy the illusion of independence!