It says hive impersonation is not enabled which means your queries will run as user which is running hive process (its usually username "hive") instead of the user who submitted the query. So if you run hive shell as "dnyanesh" your query will still be run as "hive" which is a security flaw in case you want to trace down who ran what queries.
To get rid of the warning, you should enable Kerberos and then enable impersonation (impersonation will work without Kerberos also).<property>. set following property to true in hive-site.xml
<description>Enable user impersonation for HiveServer2</description>