Keep the tortoise warm and quiet until you can get help. At this point you will more than likely need to mimimize shock. Place the animal in a box lined with any soft material - shredded newspaper is fine in an emergency. Keep him warm and quiet while you obtain help, this will minimize stress and prevent further shock. If it is going to be a while before you can get medical help, the immediate concern will be dehydration.
Injuries permitting, soak the tortoise in shallow tepid water for twenty minutes.
If available you can add electrolyte solution such as Reptimed or a similar product to the water. Ensure that the level of the water is not so deep that his nostrils are submerged. Try and observe if he drinks, as knowing this will help the vet when you get there. You can repeat this 2-4 times daily if necessary until you can reach help. In all but minor wounds you will need veterinary help.