Just wondering how you are doing today - hope your eruption is going away.
Did a bit of looking but it is so difficult to find anything like you've experienced.
I was thinking that maybe the black salve manufacturer's may be of help?
I was thinking also, that since the black salve kills and draws invading growths, that is did so to this one and through the lymph system traveled and did so to any other infectious cells out there, or maybe casued die-off and the body is now getting rid of it through your skin lesions?
Also, if the black salve killed whatever it was that composed this mass, then that would make the tests inconclusive?
How's your health otherwise? Could your body be detoxing?
Anyway, these were the only two references (from the chart posted above) that seemed close to what you described were the first symptoms, but nothing I found says anything about a secondary outburst: