Mondor's disease is probably the culprit

The symptoms described are most consistent with Mondor's disease or Mondor's thrombophlebitis.

Thrombosis of a superficial vein leads to a cord-like structure in the vicinity of the fold incision. We have seen this in a handful of patients, but usually we see within one month of surgery.

Seeing it as late as 6 months is possible but less likely. Either way, treatment should be conservative with anti-inflammatories and compresses. Each and every case we have seen resolved fairly quickly with the above therapy. No surgery has been needed by my patients, although I have heard of surgeons who like to excise the thrombosed vein.