"Sounds like a concussion," the Doctor muttered, gravely. As an automatic response to Bill's comment, the TARDIS lowered the lights in the Console Room, as well as the hall leading to her room, dim enough to see by so they wouldn't falter. He looked at Bill's ankle with concern, then made a decision.
"Wait a minute," he told her, and then when she stopped walking, he bent down and picked her up, cradling her in his arm. "You're moving far too slow, this way's faster." He tried to make it sound he was annoyed at Bill and not concerned - don't show how concerned he was, that was his unspoken rule.