Small dark speck on tongue?

Hi, I'm a 21 year old male who while otherwise healthy, have developed a pinhead sized dark spot towards the middle and close to the tip of my tongue. It doesn't hurt and isn't noticeable unless looked at close up like in a mirror. It looks black when under normal light but when a flashlight is shined on it, its more a dark brownish color. I tried brushing it off with a toothbrush but it didn't move. I've been an irregular smoker for about 4 years, usually not having more than 4 in a day and some days none at all. I've also been able to go without a smoke for weeks or months on end. Still trying to kick the habit. I also usually drink 3 or so beers a day, more on the weekends because well, my roommates do. Anyway I JUST noticed it half an hour ago and have never had something like this before from what I know of. I didn't notice it when brushing my teeth this morning. I ate some hot soup went out for a bit, came back and checked in the mirror for a cavity filling that could use refilling and BAM, there was this dark spot.