I am not talking about Hanuman bringing the Sanjivani herb. Were there regular doctors attached to these armies and how did they treat the injured?
Sushena, was a physician for Vanara army. He is father of Tara. He healed wounded Vanaras with herbs and removed arrows pierced into the bodies of the warriors.
Having thus consoled Lakshmana and having embraced him, that Rama who was born in Raghu-dynansty, was duly delighted and by calling Sushena, spoke to him the following words: "O highly intelligent one! You attend upon this wounded Lakshmana, who is fond of friends, so that he will become perfectly well in health."
Let Lakshmana along with Vibhishana be quickly made free from pain caused by the arrows that have penetrated into their body. Let all others too among the gallant bear and monkey-warriors fighting with trees who have fought on the battle-field here and stand pierced with arrows and wounded, be healed in the same way with great care."
As commanded by Rama, the great-souled Sushena, the monkey-chief gave an excellent medicine through nose to Lakshmana. Inhaling the odour of that herb, Lakshmana became healed of the arrow-wounds, free from pains and his wounds got completely cured. As per the order of Rama, Sushena then treated his companions like Vibhishana and others including all the monkey-chiefs.[Yuddha Kanda Sarga 91]
He is the one who suggested Hanuman to bring the medicinal mountain for the second time when Lakshmana fell unconscious due to the blow of Ravana's javelin. Besides him, Jambavan was also knwledgeable with the medicines but Sushena is considered as monkey physician.