If you are asking yourself: “Do I have to be PCI compliant as a merchant?”, I’d love to ask you something in return first:
Do you accept credit or debit cards from your customers? That is, any kind of cards from Visa, Mastercard & Co?
If yes, you must (should) be certified according to PCI DSS.
If, on the other hand, you do not offer your customers any payment options with credit or debit cards, then you are not obliged to be PCI certified or PCI compliant.
Regardless of this, I would still recommend that you look into PCI DSS and its security features. The reasons for that you can find in this article.