Confusion about currents in switching circuit using flyback diode
The 50A spike is being caused by the turn off switching time of that diode ~250nS. It is still turned on when the MOSFET turns on. So initially you have almost a short to the rail. 

Use a much faster diode. 

Once you get rid of that the auto-scale should allow you to see the actual MOSFET, source and fly-back currents.