Hello and welcome to the forum. I am sorry you have this worry but am glad you are under a doctor's care. Please let us know what the biopsy reveals. We want you to know that many tumors on the skin are benign or non cancerous. This article has a list of those https://www.webmd.com/skin-problems-and-treatments/skin-cysts-tumors. Things like warts are considered tumors, Seborrheic keratoses, Dermatofibromas, and lipomas. So, there are numerous things this could be. I would not worry until you need to as the odds are it is on the benign list of tumors. Please do let us know the results.