If it wasn’t a barrier between the water and your skin, the ghusl is valid.

Sometimes we have dust marks (not najasa) on our feet that don’t go even after pouring water on them. They have to be rubbed with the hand. During ghusl for major impurity I forgot to rub my foot with hand but I poured lots of water on it even between toes. Much later i saw little dust marks. This was not impure & it didn’t stop water from touching skin. Is my ghusl valid or invalid?