As soon as she saw that the healing potions were starting to help her son, from how he touched her arm, Narcissa stood and pointed her wand at him. With a, "Wingardium Leviosa," she levitated Draco and floated him back towards the manor.
Narcissa took Draco directly to her bedroom, as it was one of the warmer rooms in the manor, and she'd had a fire burning for hours. And she didn't want him alone in his suite, even after she'd healed him — if she could.
But Narcissa was sure that between herself and the excellently stocked potions closet that she would be able to help her son, better than St. Mungo's could. Ever conscious of her family's reputation, even at a time like this when she was terrified for her son's life, Narcissa knew that if she could help him, Draco wouldn't want to be subjected to the indignity of going to the hospital.
Calling for another elf to bring more potions, Narcissa started a basic diagnostic spell on her son. She'd learned such things during the First War, and was pleased to see she remembered, but not pleased at why she was having to remember them. First her husband, and now her son. She also cast a spell that would reduce the swelling of his lips and jaw, so that he would be able to swallow more.