Not a lawyer, but there are lots of intricacies to this. You can own a trademark without having it be a registered trademark. Registration is expensive and then you are expected to actively defend use of your trademark. Be prepared to pay lawyers to send cease-and-desist letters to parties using your trademark for financial profit. Not to mention you have to be/become a business engaging in interstate commerce using this trademark.

www.uspto.gov/trademarks/basics/what-trademark

www.uspto.gov/trademarks/…/how-much-does-it-cost