It is scar tissue probably caused by a fungus. Once there those marks will not go away. Cold

and damp conditions without enough air movement encourage the fungi or bacteria (I am not sure which) to strike.

You could try cleaning your plants with eco oil as a preventative and make sure there is enough air movement around the pots.

Ok great will do thanks! Just spoke to the nursery I bought it from & they suspect it to be caused from a moth that lays it's eggs & then the little holes are caused by the maggots escaping. Once there's holes the cycle is over & the black lesion should dry up? Will see...

Yeah it was definitely caused by a little moth that layer it's lava in there, ended up cutting the patch open & found 3 grubs (maggots) in there, cleaned it all out & seems to be doing ok, just has a big chunk missing / scar that's drying out.

Where do you live? Please provide more info.

Jane