It's reckless from Son. He's running flat out, lunges in, gets nowhere near the ball, and I'm not sure he was bothered about that because Gomes had given him a little hand in the face a few minutes before, and sends Gomes flying.
This is what happens when you lose control in a challenge, you endanger your opponent and terrible things can and will happen.
Hopefully Son learns from it and thinks twice next time before he lunges full speed at another player.