White on nectarines
I'm having a little trouble viewing the blemish on the fruit closely. It appears to me that the damage may be due to feeding by thrips, rather than a fungal pathogen. However, in the event that it is some kind of superficial fungal infection (such as Botrytis / grey mold), you should be able to simply remove the skin and a layer of flesh underneath the affected area.
I hope this helps!