Coming from a long background in the medical field, and unfortunately found myself elbow deep in wounds more than a handful of times, I'll give my two cents on what we're really looking at.
1. This wound is identical in shape to the original piercing migration (however, much larger in size...which isn't uncommon for a wound to grow in size, but not shape. Considering as how the taing piercing occurred how long ago, it's not surprising that it's as large as it is at this time).
2. I highly doubt that this is an abcess, considering how identical it is to the original wound. There doesn't appear to be any infected tissue (however, there is the possibility of an abcess further in the buttocks that we cannot see in the picture, so it cannot be 100% ruled out). The drainage that he more than likely has is called 'serosanguinous' which means part clear, part bloody. This would explain Chris feeling the need to buy pantyliners, and convincing himself that he is having a period, because the drainage would be mostly likely blood tinged at the least.
3. The edges of the visible wound are well approximated, there doesn't appear to be any tunneling, and there is no sign of slough/necrotic tissue. The wound bed itself appears to be a healthy pink in color, which is good for the wound itself.
4. Considering the length of time that passed between the original piercing and what we're seeing now, it's unlikely that this wound will heal any time soon.
5. Which brings me to this point: Chris has to be taking good care of this wound, as the sheer amount of bacteria found in the area (and no, that isn't a

reference, everyone has fecal bacteria to some degree around the perineum) should have seriously taken it's toll on this wound, so with that point alone, I am both amazed (because I've seen 30+ year experience nurses do wound care worse than him), and confused at the same time.