In medical test, they usually check the Height, weight. They also check for amy visual, auditory deformities. They will take a Chest X ray to rule out any Chest infections. Hand burn is a scar and it us not a deformity or an illness. So if the rest of the parameters are good, then there should be no reason why you would not clear the Medical fitness test. All that matters is that you should be in good Physical and Mental health and be free from any deformity or disease that might interfere with performing your duties efficiently.