Blog URL Error

There is something messed up with your setup.
Why do you have the WP index.php in your root directory?
You should never have two index files in the same directory, and you already have your main index.html there.

No, I don’t have put index.php in root directory. All WP files in “blog” directory only.

In root directory, there are only five .html files including index.html which you can find at https://www.tilakbisht.com or add index.html

What about your htaccess file? The .htaccess file for your WP nice permalinks should be in the “blog” directory.

Following lines in my .htacess file

RewriteEngine on
RewriteCond %{HTTP_HOST} ^tilakbisht\.com
RewriteRule ^(.*) https://www.tilakbisht.com/$1 [R=301,L]

<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /blog/
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /blog/index.php [L]
</IfModule>

I didn’t ask WHAT is in your htacees. I asked WHERE the file is.

It is also in root directory.

That’s the problem! Read my post above.
Seemingly, you will have to “cut” your htaccess file in two:
Keep in the root the portion relating to the whole site AND have another one ONLY with the WP rewrite rules in the blog directory.

BIG Thanks!!!

Working fine now.

your .htaccess file for you blog needs to be in you blog subdirectory.