I figure out the issue.
Magento website is connected with store manager for product create/update, due to some unknown reason/configurations, some of the products got deleted from Magento website and index not happened properly.
Due to which some products left as orphans in cataloginventory-stock-item table.
When I checked the number of records in
cataloginventory_stock_item tables, they differed in count.
select count(*) from catalog_product_entity
select count(*) from cataloginventory_stock_item
I have taken the
cataloginventory_stock_item table backup, truncated
the table and once again run the inventory index from terminal.
Index run successfully now and the count of the above two tables also got match and the issue of creating product from admin got resolved, as there are no more orphan records left in cataloginventory_stock_item table.