Air carrier First Officer reported a flight attendant was slightly injured during taxi at CLT when they had to brake abruptly to avoid a collision with a truck crossing in front of them.

Narrative

We were taxiing at a highly standard and safe speed out of the back alley in charlotte from gate XX. As we were turning to the south near spot XX a truck that looked like a catering truck driving from our left to our right drove through a stop sign on the road that crosses the taxi lines. The driver clearly did not see our plane and the captain promptly applied the brakes quickly to avoid impacting the oncoming traffic. The truck then took note of us and also applied his brakes. We continued to taxi but within 10 seconds we received a call from the fore FA that the aft FA had fallen due to the application of brakes and we would need to return to gate to check in on her medical status; I was the one to take the call and I could hear her in distress over the inter phone. We immediately contacted ops and ramp to coordinate a return to gate at XY which was almost directly off of our right wing. Within 10 minutes we had a parking crew. While we were waiting for the parkers; I was on the radio with ops; ramp; and the FAs to coordinate a safe and quick return to gate. The FA advised me that she did not require medical staff to be present but that she would like an on call supervisor to meet us at the gate. I decided to ask for medical staff to meet us anyway at the gate to check her status. Once we arrived at our gate I exited the flight deck and saw the injured FA sitting on the galley floor holding her arm with a bag of ice. I crouched down to comfort her and brief her on the arriving medical staff. She was coherent and seemed to be emotionally and medically stable. I did a thorough walk around to inspect for any damage and did not find any evidence of damage. I especially checked the left wing and did not see any damage. After I completed the walk around I talked to the staff that had arrived to coordinate a safe way to get the injured FA safely off the aircraft. The paramedics arrived and checked on the FA and confirmed that she was stable and they were able to move her off the aircraft safely. She was taken into medical care safely and she was taken off the plane in a wheelchair.Cause: Lack of situational awareness on the part of the truck drivers as well as some better communication between the entire flight crew.Suggestions: Better training and more situational awareness for truck drivers at Charlotte. And we; the flight deck staff; should have checked with FAs to confirm their safety before proceeding with our taxi after hitting the brakes.