Could you please tell me that if one sells a banned item in your business, in this case a skin lightening cream which is supposed to be only sold under prescription is it allowed in sharia?

Rasulullah (Sallallaahu Alayhi Wasallam) said, 'It is not appropriaye for a
believer to place himself in a disgraceful position.'

To sell banned items is a crime and if one is convicted, he will be
subjected to punishment and embarrassment. However, the income from such
sales will be permissible.

and Allah Ta'ala Knows Best

Mufti Ebrahim Desai