galls are always creapy to see. I think it is Eriophyes cerasicrumena is a species of gall mite in the family Eriophyidae . They produce galls on black cherry plants.
So its an insect gall not bacterial or fungal.
I have to wonder if its not a hybrid from Pin and Sweet cherries. Are all of the local Pin Cherries similar or are these standouts?