Plum and Cherry trees can get 'galls', and "Black Knot' disease,which look similar, which are fungal. Figs are not in that family though. Hopefully the blackness on the tree you have won't get worse. If it is fungal, it is probably contagious to other trees like itself. If the blackness continues to spread on the tree to the point it will surely kill it, then it should be burned. But first try repotting before the black spreads further. There are anti fungal sprays you could try.
I would try repotting the tree in a bigger pot (not plastic) with fresh potting soil and amendments. The reason I say "not plastic" is because of the chance your tree is not reacting well to plastic affecting the soil.
The lumpy formations on your tree look like gall which won't go away, but the blackness is probably the biggest concern.