Grind flat with dddp tools
and then either have a brlightly shining field
However, I would not be 100% certain that when you grind away it is stable and dense enough to allow you to smooth it out. It could be so crumbly in there or have a deep, soft BD cavity that you end up with a giant pit in the field
So what is worse?? The mucuousy blob you currently have or a big pit??
I would be very wary myself as head-cold aside it is a nice coin as is.