The best advice I can give you is to let the black stone share with you its meaning in its own time and its own way. If you can tolerate the ambiguity of not knowing, you’ll get more out of the symbol. (People who do best with their intuitive knowledge and creativity are people who can stand not knowing “the answers” for extended periods of time, and don’t have to tie everything up quickly in a neat bow...). Whatever this stone means, it is indeed highly personal. This is your stone.
I’m leery of those books that claim to tell you, "If it’s a small, black stone, it means thus and so..", and I’d encourage you to be leery too. And that goes double for those charts that purport to define, in very simple terms, what our illnesses mean ("If you have a kidney infection, it means you are ‘pissed off’.." . I mean, c’mon! We are complex beings and our issues are not amenable to simple, reductionistic, universal interpretation, no matter how relieving it might be to get "the answer" or an answer.
So my advice is this: Hang out with your stone, talk to it, contemplate it, enjoy it, hold it, feel its weight, texture and shape in your hand, and just sit with it, letting it show you what you need to see, tell you what you need to hear, and express what you need to comprehend, in its own way. And this will be your own way. There are no wrong answers here - just trying too hard for a quick one.
Good luck and have fun with your stone.