Ay, normal lang yan sa newborns kaya don't worry! That's usually just milk residue or skin buildup from spit-ups and sweat, a few of us had the same concern with our babies at that age, haha. I just gently wipe it with a soft, damp cloth during bath time or after feeding, and it goes away on its own as they grow. But if it looks like it's not going away, spreading, or looks inflamed, better check with your pedia just to be sure it's nothing else like fungal infection. Keep that neck area clean and dry, especially sa likod, at you'll be fine!