The black pigment appeared as a red swollen burn in the beginning

May I get the expected diagnosis, or procedure to diagnose.
The black pigment appeared as a red swollen burn in the beginning, then turned to black. Itchy sometimes. Patient history of viral infection. So could it be related to any blood malignancy?
Tq in advance

? Fixed-drug eruption

I thought about it, but when the spot appeared the patient was not taking any medication.

Targeted drug allergic lesion’

Either one of the above diagnosis, any treatment?

Fixed drug eruption

Fixed drug eruption thr is no accurate treatment to depigment the area