Where to Find and Catch Pignite
From Pokemon Go Wiki
Pignite are found and captured in Nest and Habitat locations.
Nests
Pignite Nests are locations that consistently spawn Pignite.
Habitats
Pignite Habitats are spawn locations where Pignite is likely to be encountered, but not guaranteed the way a Nest is.
Additional Tips and Information
Best Nests
If you know a really good nest or any of the nests above is really good, list them here: