This could be a diaper rash as this is common in the groin area. Diaper rash can be caused by continuously wet diapers, infrequently changed diapers, and using plastic pants to cover the diaper.
It is a skin irritation caused by prolonged dampness and the interaction of urine and feces .
Keep the skin dry. Change wet diapers as quickly as possible. Allow the baby´s skin to air dry as long as is practical.
You can apply an ointment made of Zinc oxide paste to soothe the area of irritated skin.Powders such as cornstarch or talc should be used cautiously, as they can be inhaled by the infant and may cause lung injury.