Have a tip of pen size mole on lower thigh since birth,white in color,last 6 months got twice as big and is darker worry? see doc?

Do get checked. Yes: The recent change in size, though not necessarily serious, should be examined. Your physician may have a dermatologist do an extensional biopsy to diagnose and treat.

Evaluation: I would have it evaluated if it has recently changed in size or color.

Needs biopsy: An enlarging or changing mole should be addressed by excisional biopsy. See your dermatologist or plastic surgeon to have it addressed. The obvious concern is a change or dysplasia in a mole which can lead to melanoma.