Britney Spears Driving with Severely Injured Foot, BF Paul Soliz with Her

Britney Spears ' swollen right foot -- the one she says might need surgery -- can still put the pedal to the metal ... she's back behind the wheel, despite the severe injury.

Brit was tooling around Thousand Oaks, CA Monday in her white Mercedes-Benz less than a week after her drama at the Chateau Marmont ... where paramedics showed up, and she sustained the injury to her foot.

TMZ broke the story ... the pop star and her BF Paul Soliz were at the famed Sunset Strip hotel last week when they got into an argument in their hotel room, which spilled into the hallway.

Several hotel guests heard Britney yelling and screaming, and some thought she was having a mental breakdown ... which is why paramedics were called.

As it turns out, Britney had badly injured her right foot -- she showed off the bruising and intense swelling the next day -- and on Monday she said it might require surgery. Still, she took the foot out for a spin.

Perhaps it was too painful for her, because at another point in the day ... Paul was in the driver's seat while she rode shotgun.

Britney says she's annoyed photogs got shots of her outside the Chateau last week wearing only shorts and covering her bare chest with a pillow and blanket. As a result, she said, "I'm going to treat myself this week!!!"

No clue what exactly that means, but the treat probably shouldn't involve driving on that foot.