I've had a couple of tattoos heal badly, including a black and gray one. I don't think it is infected yet. If it oozes pus or a red circle starts emanating from it and keeps getting bigger, I'd see a doctor. As it is, I'd just keep your hands off it and don't pick.
You will probably have to get it touched up, however, once it is fully healed. That's what I had to do with the black and gray bird on my leg after it did exactly what yours did.
I've only had one tattoo actually get infected, and that's because my skin just rejected the main color in it completely. I got an antibiotic shot in the ass, and I eventually healed. It had to be totally recolored, however, because the color actually FELL OUT. Completely. My artist was baffled, but he used a slightly different color, and it was fine.