Recover datafileon primary DB from the backup of the Physical Standby

validate the datafile in Physical standby DB which corrupted in primary DB
validate check logical datafile 2;

Backup the datafile on Physical standby DB
backup as copy datafile 2 format '/app/oracle/sysaux01.dbf'

In Primary DB, make the corrupted the datafile offline

alter database datafile 2 offline;

copy the backupon primary DB server and catalog the datafilebackup

catalog datafilecopy '/app/oracle/sysaux01.dbf'

Using rman, restore and recover the datafile in primary DB
restore datafile 2
recover datafile 2

Bring the datafile online after successfully restore
sql 'alter database datafile 2 online';