I got sunburned a few months ago, had a t shirt on and the skin on my left arm from just above the elbow down turned red, never hurt somehow, and at the end of the healing there was just a slight bit of peeling

Now I have a smooth one shade darker than my skin 1 inch circle of discoloration on the top of my shoulder right over the joint, I also have lichens sclerosis which could easily be the culprit.

How fucked am I? Could I actually have skin cancer on a part that didn't even get burned? Can you get some skin damage through the shirt, and then get nailed with skin cancer on the part that didn't turn red?
I've already got an appointment with a dermatologist on wednesday but I wanna hear you guys' take