Encountered a MongoDB warning after converting a replica set to stand alone server

I encountered the following warning after converting a mongodb replica set to a stand alone server. I did rs.remove('host') and removed the replSet arguments when starting the mongo db.

[root@sam ~]# mongo
MongoDB shell version: 2.4.3
connecting to: test
Server has startup warnings: 
Tue Jul  9 17:18:46.076 [initandlisten] 
Tue Jul  9 17:18:46.076 [initandlisten] ** WARNING: mongod started without --replSet yet 1 documents are present in local.system.replset
Tue Jul  9 17:18:46.077 [initandlisten] **          Restart with --replSet unless you are doing maintenance and no other clients are connected.
Tue Jul  9 17:18:46.077 [initandlisten] **          The TTL collection monitor will not start because of this.
Tue Jul  9 17:18:46.077 [initandlisten] **          For more info see http://dochub.mongodb.org/core/ttlcollections
Tue Jul  9 17:18:46.077 [initandlisten] 
> 

Please help. Need to fixed it immediately. Thanks.