I am a black African, a year ago I noticed Two hard black smooth bumps of rount and Oblong shapes on my legs and foot now I have developed nearly 30

especily on my Buttocks and my inner buttock lip has six of them joind together and 5 on my buttocks skin and about12 on my left hand two under my left arm 3 on my belly and 4 on my upper back. They are very ichy. Some also settles in my old scars. Please what coud it be? I have been to Hospital where they conducted abiopcy but yet they found nothing is what I was told.