Thank you for your message, I would be more than happy to help you out today.
Congratulations on getting your first sale, this is a huge step when launching an online shop. Since you have made your first sale, your currency options would be locked into the currency you made your first sale with.
We can certainly help you change your selling currency, however, there are some things to keep in mind before doing so.
If you still want to move forward with your currency change, you will need to reach out to us directly so we can help you make that change. While we’re not able to provide account-specific support via the Shopify Community at this time, we’d be happy to continue assisting you through live chat, email, or callback. Please visit our Help Center here and log in to your account to create a support request. Once you reach a live support member they will be able to help you get your currency changed!
I hope this helps you out moving forward, feel free to reach back out here if you have any questions, we are always happy to chat.