Gifted Apprentice by Nicholas A. Rose
Summary: Sallis ti Ath lies seriously ill and only a touch-healer, usually the preserve of the wealthy, can save his life. But when Elvallon heals the sick boy, he reveals that Sallis is Gifted, one of the few born to touch the power that allows the universe to exist.
But the boy’s skills turn out very differently from anything Elvallon expected.