The only reason you would need to associate a licence with your blog is if you want others to be able to take and use your material on other sites.
Without a licence, it falls under the copyright laws of one of:
- The country in which you reside
- The country where the server you publish on resides
- The home country of the company that owns that server
- The country where the person who takes your content resides
- Somewhere else
Resolving that needs the services of one or more lawyers, but most countries are signatories to the Berne Convention
Licenses are about about relaxing your copyright protection in a way that you control.
The other thing to consider, unless you publish on your own server, is that the blog service you use may stipulate a licence in its terms and conditions.