It happened Monday night at an apartment complex in Norlina.
A frantic Shakita Williams, 26, told a 911 dispatcher it was an accident.
"I forgot that I had left him sitting on the side of the car instead of putting him in first," she said through tears.
She said she was trying to load trash into her car to take it to the dumpster when the car grazed her baby boy's head.
Williams said over and over again in the 911 call that she was sorry. The child died Tuesday afternoon at the hospital.
The district attorney will decide if charges will be filed.