My interpretation is that the light within us, the soul Jeev Aatma is Waheguru ji's light and it because of his hukam we are here. However Waheguru is distinct from his creation even though he is within creation. Creation is a form of Waheguru but Waheguru ji resides in Sach Khand where he takes care of us as Maharaj reveals in Japji Sahib.
Creation i.e. us are not Waheguru alone because we don't have the strength of Waheguru ji.
Waheguru ji is an infinite being, all powerful, all loving, eternal, ever present, immaterial, spaceless, Atemporal/ timeless being.
Since Waheguru resides in Sach Khand (so in a sense he is not only Andhar wala, but also Upar Wale because he resides in a higher spiritual plane, the realm of truth) some may ask how is he everywhere? We can answer this with an analogy. Just like how the sun's rays hit earth from millions of miles away, Waheguru ji's light permeates throughout Sach Khand and into Dharam Khand (where we are) and all throughout creation.
This is a very interesting topic and Basics of Sikhi are do a new series on Braham Vidhya and it cover this in much more depth.