These ants appear to be guarding the flower buds, are they? Or are they hurting it?
2 Answers
No, the ants are not hurting the peony buds or plant in any way. See this answer to a similar question for an explanation.
The ants are fine, as already noted.
The shriveled bud may be an indicator of poor overall health in the plant, rather than "damage, as such" - I have some peonies in marginal locations that will produce "dud buds" like that - a half-hearted attempt that never makes it to being a flower. Of course, I don't know what your's looked like before this - there might be some sort of damage going on, but my experience suggests "improve soil and/or light condition for an overall healthier plant" as being the root cause for similar things that I see.
Though zooming in, that looks more "eaten" than I gathered in the zoomed out view.