SSH login failed after setting up password for Same ssh user

SSH login failed after setting up password for Same ssh user

I am working on EC2 client. I have setup user account and respected
public/private key for SSH login. It was working fine. Today I had to
install ftp so that I can upload files through filezilla. SO instead of
creating new user for vsftpd I setup password for same user (user which I
was using for SSH). Now I am able to access FTP using same credentials but
my SSH login is failed. It throws me error as "Disconnected: No suppoerted
authentication methods available (server sent: publickey)". Now I am not
able to access my ec2 instance using SSH at all.