If there's a black spot in your scab, it could be from the electrocautery device used to stop bleeding. Some of my own mole biopsy sores, when new, were pretty bad looking, for a while.
Now, I'm going through a little melanoma concern of my own, too; and I know better. I had a normal and stable mole, on my back, removed in September. The dermatologist was removing a few others, and I asked for this one, for cosmetic reasons. Now, a couple months later, I see that the scar has pigmentation growing through it already. It was only a shave biopsy, and this was a pretty big mole. The pathology result was benign. The new pigmentation in the biopsy site looks darker and abnormal in shape. But, I knew this could happen, and still, my anxious mind has me worrying about it anyway. I should have left it alone, I guess.
So, I'd say don't get into the idea of removing absolutely everything, unless they're highly suspicious and the dermatologists insists. I also know waiting on these results can be very tough. Your situation doesn't sound horribly concerning. Try to hang in there.