A320 Captain reported a fume event characterized as 'dirty socks' upon gate arrival.

Narrative

The flight departed and everything appeared normal; we landed in ZZZZ no issues in the flight deck. Upon arrival at the gate and after we shut the engines down the APU had just finished its start sequence. We were notified that the flight attendants in the aft of the aircraft smelled dirty sock odor on final. About the same moment my nose felt on fire. I shut the APU bleed down immediately. Fortunately we had a very light customer load; so we had mostly deplaned. By the time I left the flight deck the cleaning crew was on the plane. I had them exit as soon as possibly. Out of an abundance of caution for their safety. We opened all normal exits and flight deck window in an effort to vent the plane. After exiting three of the four flight attendants had bad headaches and [name] complained that their esophagus was burning. I had my First Officer [name] call the Tower for medical assistance; and informed [company] personal on the ground we needed medical assistance. Once the GPU was plugged in I shut the APU down. FO (First Officer) and I remained with our inflight crew provided water for them until the medical personal arrived.