Question

what is SI unit of pain

Answer 1

pain is not a quantity which can be measured so it don't have any SI unit.

Answer 2

Harvey's group had a noble goal: creating an objective measure of human pain. They devised a unit for the intensity of pain, which they named the dol, with the name coming from the Latin word for pain, dolor. Ideally, the measurement would be applicable regardless of the type of pain.