On Sun, 18 Oct 2020 02:01:18 +0530, Palash Nigam said:

> While building a new kernel i forgot to change the name of
> CONFIG_LOCALVERSION in the .config file as a result my current kernel got
> replaced by the one I was building. 

Hold that thought for a moment...

> My original kernel still exists as Pop_OS-oldkern.conf, 

That would be a config file, not the actual kernel.  Unless Pop_OS has a
*really* bad naming convention for things...

> and I can still boot into it once booting into the new kernel fails.

If you can boot into it, it can't have been replaced.  So you've done something
to your system, but it's not what you *think* it is.

What does an 'ls -l' of /boot say (definitely need to check timestamps
on files)?  And are you using grub2 or something
else to load the kernel?