it's not the bowden cable as mentioned in the previous post since you used the inside handle to open the door. it's likely to be the cable that connects the outdoor handle to the door lock actuator. it isn't that tough to replace but it takes time and i wouldn't want to be attacking this if it's freezing out since it's a tight space in the door and will require bare hands.
it requires removing the door panel and then getting to the actuator. here's a pic that shows the actuator and its connections. my guess is that "C" broke.

"A" connects to the "button" you see from the inside of your car that's up when the car is open and down when it's locked.

"B" receives the end that is attached to the key cylinder. i.e. when you turn the key, this white receiver rotates.

"C" gets pulled up when you lift the outside handle

"D" gets pulled when you pull the inside handle

both C & D are pulled by a cable similar to the brakes on a bicycle. in both cases, you can see the part that holds the cable sheath.