Whatever you do, don't let any dentist probe it with his silly metal pick. That's how my same problem got worse and had to be filled a few years later.
Have you read Cure Tooth Decay? Ok you won't repair the enamel but you should be able to remineralize over it if you have some of that Butter oil and cod liver oil he talks about.
I hope I'm not the only one to believe in it, I've just started doing this. I already hardly have any carbohydrates or sugar, so his advice isn't too hard to follow for me.
Also, I'm starting using a toothpaste with Novamin in it (look up online which toothpaste with it is available in your country), but it has glycerin in it, and although I haven't seen any proof, some people say it's bad - although in the case of Novamin, that might be good that a transparent film stays on the teeth. I'm going to alternate between this and MI Paste, in case I can put all the chances to remineralise those root caries. Yes, that's what it's called. If that's just a little spot, surely all this should work for you if people aren't talking BS about remineralization.
I also heard that if the spot is very dark, then the decay is inactive - would be nice if someone could confirm, I'm fairly new in the world of dentistry knowledge.
Also, make sure you don't brush too hard, my root caries have developed recently because of that.
Please if you try anything let us know how you get on. So far after a week, I feel like my new decay is slightly less visible, but maybe that's in my head - the discoloration isn't expected to disappear with remineralization.