Unfortunately, I am not an expert with this. I do know they discuss this condition alot in the Peds forum; try posting there too if you have not already.
Thank you for your question. Usually, in new born such hair tufts may appear as congenital variation and not harmful if remains present lifelong. However, most of the times they disappear after 6-8 weeks after baby is born. Therefore, wait & watch policy is best in initial few weeks to understand this tuft's nature. I would recommend that you consult his treating pediatrician after 6 weeks, if it won't disappear of its own. Hope this helps.
Could you please updated? My child is born with similar tuft of hair. Ultrasound looks normal, need an MRI at 6 weeks.