The pilot reported that after landing with an 8 mile-per-hour crosswind, his left foot became lodged under a rudder pedal. The airplane drifted off the runway pavement; he was unable to correct because of the soft turf condition. The nose landing gear subsequently dug into the ground and the airplane nosed over. The airplane sustained substantial damage to the fuselage, left wing, and vertical stabilizer. The pilot reported that there were no failures or malfunctions with the airplane prior to the accident.