When you delete a site on Netlify, the subdomain name can sometimes take a bit to fully release from the system. A few things to try:
Wait 24-48 hours after deletion, then try renaming again. The name release isn’t always instant.
Go to Site configuration > Site details > Change site name on your current site (dhirsatra01) and try entering “dhirsatra” there.
If it’s still showing as taken after 48 hours, it likely needs a Netlify support team member to manually release it from the backend.
You might also want to open a proper support ticket at Netlify Support with your team ID and the site name you want released. They can usually sort this out fairly quickly.
In the meantime, your site will work perfectly fine under the dhirsatra01 name, especially if you’ve got a custom domain pointed at it.
It sounds like the original site name hasn’t fully cleared from Netlify’s system yet. Sometimes deleted site names take a bit of time to become available again. You can try waiting a short period and then renaming your current site, or contact Netlify support to fully release the name so it can be reused.