I am using Tornado for a small blog which may get around 500-1k visits / day , is it ok to use tornado without any proxy in front of it ?
Yes, and no
If you start Tornado on port 80, you can use it stand-alone but you shouldn't. Tornado is really bad at static files, it wasn't built to serve static files, and shouldn't be serving static files, it was put there just to make things a bit easyer during development. You'd be much better off putting an NGINX instance in front of your single node, as described in their documentation.
NGINX also gives you lots of other features like static caching, easy header manipulation and better logging/error handling