A mole is generally a pigmented nevus, and a sudden growth of a mole on the left hand can be caused by trauma, sun exposure, or by a chance abnormality of unknown origin.
A pigmented nevus is a benign skin growth that is associated with a variety of factors acting on the skin. Long-term sun exposure, localized trauma, body hormone metabolism are all related, and long-term application of glucocorticoid drugs on the skin is also prone to appear. Some people have more moles than others, this is related to genetic constitution.
Pigmented moles have no effect on the body and have a relatively small impact on aesthetics. Moles growing on the hands can be left untreated if there is no tendency for malignant changes, but pigmented moles growing on the palms of the hands, the belly of the fingers and other parts of the body that are susceptible to friction and extrusion, in order to prevent malignant changes, it is best to go to the hospital in time for surgery to remove them.