I think you should have printed a cowboy hat and glued that on. I’ve seen people do it, and it hides the line very well 😆

I’m not sure if there is an easy fix if you want to continue. My prints often come with a slight warp underneath (from the bed). That leads to the exact same result as in your picture. Maybe that’s fixable on better printers. Or you’d need to print just the hollow outline that gets glued on. Not any middle part that could be warped slightly…

Or some postprocessing. Fill the gap with filler from the hardware store before painting. But that won’t be possible with multicolor prints.