No, you don't need a trademark to use your logo to label your products or services. However, using an unregistered logo could expose you to the following threats:
- Other brands might violate your brand's identity by adopting a logo closely resembling yours.
- You have no protection against someone outright copying and utilizing your logo.
- There's a possibility that someone else might register a trademark for your (or very similar) logo before you, putting you in a position where you are the one infringing on their trademark. You may be unaware of this until receiving a cease & desist letter.
Therefore, we strongly advise considering trademarking your logo (or your brand name) as soon as possible.
Bear in mind your brand doesn't have to actively sell; you can secure the trademark for a future business venture. Just be sure to submit a final version of your logo since you won't be able to make changes to your trademark after applying.