trademarking a makers mark

Hi, my name is Amanda Lee, and I just graduated with my BFA in Metals and
Jewelry in December. I have spent the month of January making some jewelry,
and I would like to try to sell it. But before I do, I need some advice
about makers marks.

I have been working in sterling silver and have stamped my work .925 to
indicate the content and also have stamped it with my makers mark (logo).
All of the designs are mine, and I did all my own work.

I am currently visiting a friend who has a contact in a very upscale jewelry
boutique. The owner of the boutique sells a lot of handmade jewelry from
artisans around the country. He told me that he liked my work ("it's
unique"!!!), but if I want to sell to him, then I must obtain a trademark
for my makers mark. He said this is because I live in a different state
from where his boutique is located.

Is what the owner said correct? Do I have to trademark my makers mark
before I can sell my jewelry outside of my own state? And if so, can you
tell me how to trademark my makers mark? I don't know the first thing about
how or where to apply for a trademark.

Thank You.