Good day. my six week baby girl has extra phalange on her little finger, together with extra tiny digit that looks like skin tag. should i be worried?

Not particularly: Such "accessory" digits are a common birth anomaly that can be passed by autosomal dominant inheritance with a tendency to miss or skip generations. I routinely tie the tiny ones off at the base, cutting the blood supply so it falls of eventually. Those with full extra digits are often have them surgically removed before school age. Discuss with her doc.

Extra fingers: Skin tag like extra digits are fairly common. X-rays can be done to demonstrate if there are bones inside. Usually nothing need be done immediately.