In God’s plan there will be a time in the future when his faithful people will be made immortal and there will be no need for their bodies to be healed because they will never be sick. At the present time, however, our bodies suffer from illness and disease and injury, and it is one of the wonders of creation that in many cases our bodies are able to heal themselves. And, of course, the process of healing has been greatly helped by the medical profession and the generations of people who have devoted themselves to searching for cures. The body will need healing for as long as we remain mortal, but when Jesus returns he will make his faithful people immortal.
There are prophecies about what our bodies will be like then:
… from [heaven] we await a Savior, the Lord Jesus Christ, who will transform our lowly body to be like his glorious body, by the power that enables him even to subject all things to himself.
He will wipe away every tear from their eyes, and death shall be no more, neither shall there be mourning, nor crying, nor pain anymore, for the former things have passed away.