It’s giving me an error 'Could not connect (port 8291) - connection refused.
I am sure password and username are correct.
How can I log on again through winbox please.
Try Winbox 3.11.
https://download.mikrotik.com/routeros/winbox/3.11/winbox.exe
Try Winbox 3.11. You can download it from the usual download location by modifying the version number in the URL.
Is this device reachable from the Internet?
http://forum.mikrotik.com/t/winbox-vulnerability-please-upgrade/122004/1
It seems your Mikrotik is infected. You need to locally login and disinfect that Mikrotik.