The Korean international looked like being the villain when he lost possession in the build-up to Birmingham's 85th minute equaliser from Kevin Phillips.
But the summer signing from FC Seoul made amends two minutes later when he was first to react after a Matthew Taylor free-kick had struck the woodwork.
Megson said: "Chung apologised for his part in gifting them the equaliser but then had the presence of mind to be in there for the winner.
"It was a quality piece of finishing. If he had struck his shot first time I am sure it would have been blocked by the keeper.
"But he had the composure not to panic. It was a terrific finish and it was fortunate for us that the opportunity fell to him.
"He is doing well. He actually turned the game for us against West Ham in midweek and we know what we are getting from him.
"We sometimes struggle with his Korean accent but as a player he is getting stronger and better."