Hi @PANUGANTI_RAVINDER and welcome to the forum,
No bug here… Priority isn’t a built-in Asana field like Assignee or Due Date; rather it can be added as a Custom Field to any project.
To do that, click “Customize” on the right side of a project, find Priority on the Fields list and toggle it on to include in the project.
If it’s not on the list, you can click “Add field”, then “Choose from library”, then select it from the displayed list of existing custom fields to add it to the project.
This will get you a field with values of High, Medium, and Low. If you want any different set of values, you’re free to create your own new custom field containing any type of prioritization you’d like.