World number two Nadal was forced to play his second round match with two bandaged fingers on his right hand after burning them on a hot plate at a restaurant in Ohio.
"I got burned. I had a little bit of accident in a restaurant a few days ago," Nadal told reporters after beating Frenchman Julien Benneteau 6-4 7-5.
"It was an accident. The plate was very, very hot and I got burned," added the Spaniard, who said the blistering was causing some discomfort during play.
"A little bit. If you see the blister, you can imagine. I am going to show you now," he said with a grin.