To tell the truth, he's not completely sure either. Well. He wasn't when he started mentioning about the hair. Now that she's floated the idea that she could very easily stop, it's dawning on him that he doesn't want her to do so.

"No, I ..." Han shakes that shaggy brown hair of his. "I don't want you to stop."

It just so happened that one of the only person he ever felt loved by happened to delight in ruffling her fingers through his hair fondly. A surrogate mother who was no longer around and every time Han thought of her - it felt as if his heart was being squeezed in a vice. Never mind the fact that Han Solo still has no idea what to do with the thought of someone deeply caring for him.