In Pokémon Sword and Shield, when your Pokémon are hurt or fainted, you generally take them to a Pokémon Center. In The Isle of Armor, however, while the train station has a sales clerk and you can also buy items from the watt trader, there isn’t a traditional Pokémon Center on the isle.
That said, once you get to the Master Dojo, there is a way to restore your Pokémon.
Once you make your way through the introduction of the Master Dojo, you are shown a room to the right side of the dojo that gives you two options.
You may use it to change your clothing the same way a changing room in a boutique would allow you to do, or you can use it to restore your Pokémon to full health, the same way a Pokémon center would.
Be sure to visit the dojo and heal your Pokémon often as the Pokémon on the isle are rather strong, and there is a lot of ground to cover. If you are far away when your Pokémon team gets low, you can fly to the dojo via Fields of Honor stop on the town map.