You can cut it out and pray it has not spread. Usually by the time you can see it, it's already propagating and spreading.
There are no sprays that work. All the nonsense you can read about simply is a pipe dream - milk, 'cornell' formula, h2o2 etc... all you'll do is spread it around even more with the drips.
And, in flower, you don't want to spray any of that shit on buds anyway.
so cut it out, bag it immediately, because a plume of spores is happening as you do it. Take more than necessary off - anything that may have come in contact, like nearby leaves.. maybe a whole side branch if more than just 1 leaf with a spot etc. pray you don't see spots in the coming days.
if it's only on one plant, which is nearly impossible to be certain of, think about isolating or trashing that plant. If the colony was large, there's a good chance it already spread and you cannot see it yet. if you cut off a leaf with a tiny spot on it, you can be a bit more optimistic.
"Rinsing" or washing buds does not clean it either. Extractions, edibles, or smoking are not an option unless you want to lie to yourself about it being tainted with fungi.