Half mole, half crater: I was getting rid of mole using apple cider vinegar.

Have you asked your family doctor or a Dermatologist to evaluate this mole or any others that may be "hiding". The fact that half the mole fell off does not necessarily mean that it is benign. Even part of a melanoma could fall off  and leave an irregular base. I would strongly suggest that you seek a professional's opinion.

I would recommend visiting a dermatologist to discuss removing the rest of the mole and to make sure  the area is not infected. Most skin growths are harmless. But sometimes—particularly in the case of some moles—they’re not and can be cancerous, which is why all moles and growths should be assessed by a dermatologist.