The version of CocoaPods used to generate the lockfile (1.5.3) is higher than the version of the current executable (1.5.2)

on $pod install it gives warning & fails

The version of CocoaPods used to generate the lockfile (1.5.3) is higher than the version of the current executable (1.5.2)

What is it trying to say ?

macOs : 10.11.6 osx el capitan

my pod version is : 1.5.3

What does"current executable" (1.5.2) means ?

and

how to update it ?