How serious is my "invasive well-differentiated squamous cell carcinoma, involving biopsy border" diagnosis?

First, I applaud you for noticing something that wasn't healing and going in to have it checked. Although invasive SCC sounds very scary, it's usually quite treatable with a Mohs surgery in that location. You will be ok. Continue to check your skin often. Now that you've had one type of skin cancer, you are prone to more surfacing over time (not because of your medications)."This answer has been solicited without seeing this patient and cannot be held as true medical advice, but only opinion. Seek in-person treatment with a trained medical professional for appropriate care."