I have added a place of interest to the map. But OSM records it as being in a neighbouring Province. How can I fix it? Where does OSM get its bearings from
’
OSM uses the boundary relations to determine the provinces and other administrative boundaries. In case the relations are missing, it falls back on nodes presenting those objects. It then looks for the nearest node, which is not necessarily the correct node.
So it is best to add the boundary relations. In many countries those have been imported from sources with compatible licenses, I don’t know what the situation is for your area.
Please add a link to a POI you have added, so we can investigate the situation better.
The FAQ on Nominatim explains several caveats of the “address lookup”.
To be pedantic, this is Nominatim, not OSM.
You can use is_in tags to make the containment relationship explicit.