After a little research, I got above error resolved. Just had to enter the command as follows:
nagiossrv root [libexec] > /usr/local/nagios/libexec/check_nrpe -H 128.19.5.131 -t 30 -c check_users -a '-w 5 -c 10'
And the output would look like:
USERS OK - 1 users currently logged in |users=1;5;10;0