The best cause of action after something like that could happen is,
Go to the hospital first, that wound would probably be pretty big if whoever did that sanded down their leg. Second carefully get the plane out of the nail/jam it's in. Third, put out the fire water, moist towelette or fire extinguisher (if in your area)
Recommendations for a greater cause of action: Wear safety/protection,
Make sure there isn't any loose nails (as the one described here) for the plane to get jamed.
Check if the plane has any safety cautions installed for these type's of problems.
Hopefully I helped you a bit.