Dermatologists will tell you that this is a sure sign skin cancer! It is the aftermath of an "abnormal mole" best defined by the "ABCD"'s of Skin Cancer Detection:
A= Asymmetry [one half of mole does not match other half]
B= Border [indistinct; ragged, notched or blurred]
C= Color [inconsistent; pigmentation is not uniform]
D= Diameter [any mole larger than 1/4 of an inch - or the size of an eraser head on a #2 pencil - is suspect].
Do you remember what the mole looked like BEFORE it fell off? (BTW, there is disagreement over whether to define abnormal moles by their appearance or a microscopic analysis of the cells). People are encouraged by the DC (Dermatological Community) to see a doctor if any mole on their body:
3. Crusts or
4. Changes shape
All moles are considered "discolored skin growths" and contain a combination of melanocytes (pigment cells), other skin cell clusters and oxidized blood. Nearly everyone has at least some moles, but people with fair skin tend to have them in greater numbers which increases their risk of skin cancers (the DC traditionally links sun exposure with their cause because 1. moles appear after birth, generally in response to sun exposure and 2. skin cancers are more prevelant in fair-skinned people who have less metabolic activity in their pigment cells and thus sunburn more easily than their darker-skinned counterparts). This is evidently viewed as a "bad reaction" to sunlight. Personally, I think there's a good chance that this could actually be a good reaction or "defensive" in nature.
Other "skin discolorations" include port wine stains, and birthmarks, which are different from common moles because (it is theorized) the skin's pigment cells (melanocytes) are not involved in these type of growths. Instead an abnormal cluster of capillaries causes the discolorations, and port wine stains and birthmarks are not cancerous.
Freckles (or Ephelides; more common in fair skin types) and liver spots (or Lentigines; common in all skin types and generally show up later in life) are still other "skin discolorations" that are not necessarily growths, but could become cancerous at any point.
Unlike the more common forms of skin cancer (basal, squamous), melanoma may appear on areas of the body which have NOT been regularly exposed to the sun and also often appears on areas of the body where there is very little or no melanin present: palms of the hand, soles of the foot, ears, nose, genitalia and even under nails.
I would consider locating the cause of this bloody mole (and seeing a dermatologist that you can trust to "partner" with you in repairing the cause - if possible). In my opinion, it is no different from a scab (only the mole is an inside-out scab) or skin tag in nature and probably similar in origin, as well. It could also be a Vitamin D deficiency (I say this because melanocytes in and the development of moles are so closely associated with sun exposure).