I Found A Small Black Mole On My Left Buttock.

I found a small black mole on my left buttock. It wasn't there before, and it's toward the bottom of the buttock. It looks like a regular mole (I have a couple moles on my body, two on my shoulders) but the size is irregular. It's small but shaped weird and it doesn't come above the skin. It's within the skin. It was not there before, it appeared within the last couple weeks and I just noticed. Is this a symptom of anything? I know I have some thyroid issues (hypothyroidism runs in my family) and I've been on Tramadol and Naproxen to help control my severe carpal tunnel.