Black stuff on tooth?

I was checking out my teeth and there was some black stuff at the area of the tooth where two teeth meet. 
I panicked and thought it was a cavity
I brushed the black stuff away fairly easy with just a toothbrush
This is what’s left of it. It’s the dark dot on the left of the pic. 
Is it a cavity, something stuck in my tooth or something else?
I know you aren’t dentists but I’m asking for people who have had similar things/cavities 

Rudy2021-01-28T18:57:08Z

If black spot on the tooth your fine could be decay but if it's on the gum could be a infection I'm no dentist your teeth look much better than mine lol .