Female Anatomy help - PLEASE

Excuse my lack of vocabulary - a testament to high school health class.

I have always had this lump inside what I think is my labia majora towards the mons pubis. It kinda moves around but like it’s tethered. It doesn’t hurt or really feel at all. It’s not visible at all but it’s like a small egg shape - I imagine a little robins egg. It is only on the left side, there is nothing equivalent to it on the right.

I’ve been to the OBGYN but have never brought it up. I’ve had it for so long I kind of forget to mention it and her focus is on the *inside* health so I don’t think she’s felt it.

Anyone know what I’m talking about?? Is this is legit part of the female anatomy and I am just super ignorant? Thanks in advance.