Army boy afraid of Dr.'s

My 17 1/2 yr old son is in the process of enlisting in the army when he graduates high school in June he will already be enrolled.He went for the all day long extensive army physical and passed everything except on his vitals his heart rate was in the 120's, yet his bp was normal.
I had to take him to family dr. 3 days in a row to get him to sign off on my son that he was ok, they put ba pulse ox on his finger and we noticed everytime a nurse or doctor walked into the room that his pulse went up at least10 beats.Thus  after questioning my son I discovered he is terrified of Dr's Nurses an Hospitals.
Trigger event I think he had to get stitches at age 8 almost cut finger bone took 5 of us to hold him down so they could give him the necessary injection to numb his wound.

Question how can I help him, hes going to have to deal with alot more with doctors in the future and he needs to be able to manage this fear/phobia.