will.i.am's and Cheryl Cole's accident happened after his Cadillac hit a parked car.
The Black Eyed Peas star and his close friend Cheryl Cole were pictured with bloodied noses after the crash, which happened in Los Angeles at 3.30am yesterday.
Onlookers said will's injury was the result of him being hit by an inflating airbag on the driver's side, while no safety system appeared to have been triggered on Cheryl's side.
A witness told The Sun newspaper: "Both seemed shaken but were checking each other over.
"They both had nose bleeds and at least one of the airbags had deployed.
"Police soon arrived and everyone was told to move back. It was only when Will.i.am stepped out I realised who he was and that the passenger was Cheryl. Will.i.am's main concern was Cheryl."
The 'Boom Boom Pow' star was taken to nearby Los Angeles Cedars-Sinai hospital, and later left wearing a neckbrace, while his pal was treated at the scene of the accident.
The parked car – which was empty – was badly damaged in the altercation.
Both will and Cheryl later took to twitter to reassure fans they were fine.
Will tweeted: "Car accidents are not dope … I'm glad I'm o.k #wiplash.
"We're fine …@Cheryl Cole were coming back from the studio but she and I are fine … just a little #wiplash (sic)."
Cheryl added: "Don't worry me and @iamwill are fine, promise."