Just keep watch on speckled naevus
This is known as a speckled lentiginous naevus or naevus spilus. The lesion is present at birth in most cases and grows relative to overall patient growth. It is rare for any of these pigmented macules to develop into a melanoma but this has been reported. Some of the macules may become slightly raised at puberty but this is of no significance.
However, should the pigmentation become atypical then the changed lesion should be excised. Generally though it is best just to photograph these and only have the patient re-attend if something changes.