The X Factor USA judge was photographed earlier this week with a plaster behind his ear while driving in Los Angeles.
Its position sparked a rumour that he had had a facelift, but his spokesperson has denied the reports, saying that he had cut himself shaving.
"He accidentally cut himself," the insider told the Daily Star.
Cowell had been spotted while driving Sunset Boulevard in his Ford Bronco.
A passer-by said: "If he was trying to hide something he wouldn't be driving past a load of photographers on one of America's most famous streets."
Earlier this year, it was revealed in Tom Bower's biography of Cowell that he has two Botox sessions a year in order to stay looking young.
The music mogul appears to have fully recovered from his recent illness, which saw Louis Walsh temporarily fill in for him on The X Factor USA.