u/Double-Cut-2886

I have just now noticed my tooth in this state. When I drink cold water it reacts with a noticeable sensitivity, not too harsh, just a sharp cold sensitivity. I had it dental filling last year but I noticed it still has a small black dot inside the filling so I shrugged it off thinking it'll go away — then months flew by and it did not go away and now it's like this. What should I do?