As you have already been given the diagnosis that it's a fungal infection.
You can use anti fungal agents like Ketoconazole. I also would like to give you some tips on maintaining hygiene and preventing any other infection.
- I suggest you try keeping the area clean, wash with mild soap.
- If you are using a steroid cream or any drug having steroids, steroid damages skin and reduces immunity of skin.
- Do not keep the area moist as it increases growth of fungus.
- Most importantly take bath every day, as there will be accumulation of dirt, bacteria and anti fungal cream metabolites on skin.