Is it better lo leave the scab alone (and dry) or try to make it fall? (photo)

Small scabs are definitely better off when left alone. Pulling off a scab can worsen the final scar in many cases since the environment under the scab stays sterile, moist for growing cells, and protected from the outside world.For larger scabs like yours, it is sometimes better to have a physician remove the scab surgically and treat the wound with dressings to speed up healing. It's not skin you see under a scab that large but tissue called "granulation tissue" that will eventually become covered with skin that will grow in from the edges. Areas where there are scabs as large as yours usually heal with thin skin and worse looking scars than the incisions around it. This can be revised in the future once the tissues soften up (6-12 months after healing). I advise you to make an appointment with a board certified plastic surgeon in your area for evaluation so you can sure you are doing everything you can to optimize your outcome.

I agree you should see a local surgeon, I sometimes remove these as they are basically hanging on and dont do what they are supposed to do and act like a "medical dressing that is sterile"

You really need to see a surgeon to help manage your complication. Generally, we would allow the dark area to fall off on it's own, but you need to seek professional advice immediately.