Hi,Welcome to HCM.
By the facts of your query,You neither have
Dermatofibroma nor
nodular melanoma on back of your left hand.
Don't treat by self diagnosis,which could complicate a simple problem in to complex issue like yours.
Nitrogen Freezing has made the skin on the lump fixed to the lump and has made its diagnosis little more difficult.
In my opinion you seem to have-
Ganglion Cyst of the Wrist dorsom.
Its a benign condition and is a histiocytoma-hamartomatous cyst form the synovial lining of the small bone joints of the wrist.
If hot fomentation/Cold compresses/Anti-inflammatory drugs don't reduce it,then I would suggest CT scan and planned Arthroscopic
laser ablation,which reduces its recurrence chances,than a open
surgical treatment from a Surgeon or Orthopedic endoscopic Surgeon.
Hope this would help you to plan treatment with your doctor.
Will appreciate hitting thanks and writing review comments to benefit needy patient visitors at HCM like you.
Good day.
Dr.Savaskar M.N.
Senior Surgical Specialist.
M.S.Genl-CVTS.