Thanks for your query.Based on the facts that you have posted it appears that you have nothing but a Ring worm infection
(Jack Itch) around groin and shaft of the penis.
Please take anti fungal medication
and orally along with anti topical fungal jelly for local application twice daily.
Ensure to clean your genitals with warm water twice daily.
Wash your inner wares in boiling hot water mixedwith antiseptic lotion like Dettol
This will get cured within a week.