Mole removal options vary by clinician. The mole you had treated should be reassessed to make sure the change is due to the treatment and not progression of the mole size or shape.
Raffy Karamanoukian MD FACS
It sounds like you have some swelling and superficial necrosis (the black change) that is common to see after liquid nitrogen therapy. This can be a common reaction with freezing. With that said, freezing is not the best treatment for a true mole. It is always best, and I recommend, that you consult with your treating provider if you have concerns about how your treatment is progressing or you are reacting--- and this may often require an in person evaluation. Be sure to have your care supervised by a Board Certified Dermatologist.