Kourtney Kardashian -- Toddler Down!! Car Door Hits Penelope (PHOTOS)

Kourtney Kardashian had a serious mom moment -- she looked away for a split second, and one of her kids took a car door to the face!

Kourt was actually holding 3-year-old Penelope's hand as they walked past a parked car in Malibu on Sunday -- and at that very moment, one of the car doors flung open.

Poor Penelope went down in a heap, and, naturally burst into tears. Mom and the nanny quickly comforted her ... and we're told she's okay.