Yes, a self-registered person (who has completed the registration process online) can change their details on the portal by following these steps:
Visit the official PM KISAN portal
Click on the ‘Updation of Self-registered Farmers’ tab
Provide your Aadhaar number and the captcha code
Click the ‘Search’ option
On the next page, click ‘Edit’
Select ‘Update’ and ‘Save’ to complete the process
Note that Aadhaar number is mandatory to access and edit the registration details.