The 20-year-old Nigerian midfielder was poked in the eye in a clash with Anthony Annan during their 2-1 quarter-final defeat against Ghana and he was forced to leave the pitch.
Mikel, who replaced Frank Lampard during the second half of the Blues' goalless draw with Liverpool at Stamford Bridge on Sunday, has revealed for the first time that he feared he had damaged his sight.
"I couldn't see when I went back on the pitch and I had to go off," admitted Mikel.
"When the ball was coming, I couldn't see it properly. I didn't swap shirts with Michael Essien after the game because of the eye injury.
"It was hurting too much to worry about swapping shirts. It's a bit better but it is still a bit painful. At the time it really hurt.
"I thought I'd lost my eyesight when I was lying on the floor but thankfully everything is fine."