I hope no one would risk the poor guy's life by wasting another 30 sec taxi (sic) off the runway instead of stopping asap and calling for a nurse/doctor - Just to save a bit of inconvenience? I hope not... If I was the Captain - or a friend or relative of his I wouldn't be thanking you for that I can assure you.
Do both, ie as long as someone is already attending to the patient, call for a doctor/medic while you continue to taxi back towards the terminal. This is an emergency with a potential loss of life. If you're a long way from external assistance why on earth would you stop!