Fungus or disease on mountain ash

What is it? I searched some but couldn't find any photos close up enough to match it. It's on a short stub where I had cut off a small branch a few weeks ago.
Should I spray, if anything? I don't see it anywhere else in the tree. I seldom spray any plants and have little troubles. When I do spray, first I try laundry soap in water which works most of the time.
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