iPhone 6s screen has yellow spot top right hand corner

I got someone to buy my IPhone 6s for me in New York (I live in Barbados). after a week of use I've noticed a yellow faint spot in the top right hand corner of the phone just under the battery icon. what can I do to fix this? Do I have to send my phone all the way back to NY 😟. This only happens after 1-2mins of use of the phone on