Hi,
As I said the issue is not with the PayPal plugin. It will allow you to pay without a PayPal account, as it does on our website (we're using that same plugin here to accept payments via PayPal and people can pay with their credit card without creating an account).
However, it's possible that because the email address that you used for the user account or the cookies on your browser, PayPal already knows you as a customer and forces you to open an account with them to continue using your credit card with them.
In any case, that's not something you can change in the settings of the PayPal plugin or in HikaShop. As I said, you need to contact PayPal's merchant support so that they can help you with your situation.