Karma could only cure himself utilizing the demonic healing power previously.
But after his training with Agyat, he could use his healing on others to some extent.
Every time a demon bit on Abhinav's flesh, he healed him in this manner.
When Karma called some low-level demons, he commanded them to nibble on Abhinav's flesh as he was awake.
And, as their master had instructed, the demons bit his flesh, clawed him with their claws, and licked him with their tongues while his eyes were open.
He told the demons to slow down the procedure because if he started bleeding, Karma might heal him with his demonic energy.
This torture lasted approximately an hour, during which time the man could do nothing except scream in anguish and misery, and his screams were not even heard by anyone.
Because, unlike Agastha, Karma cannot recover the demonic energy he uses, he must utilize it with caution.