What could this be ?

i have this dry patch on my inner thigh and it itches like hell ! it wont go away. could it be associated with an Std ?? when i leave it alone it gets very dry and flaky around it. but sometimes i just have to scratch and it gets like this.

<img src='https://patient.azureedge.net/forumsimage

it resembles Pityriasis Rosea which is treatable with over the counter medications.

what kind of medicine can i put on it?