For Google to be showing to your page with that parameter, something must be linking to it like that.
You might be able to figure out where that link is from using Google Webmaster Tools. Sign into your site and navigate to "Search Traffic" -> "Links to your site". From there, look in "Your most linked content" and try to find that URL. Click on it to find out where the links are coming from.
If you use Google Analytics, you might also be able to find it there. Navigate to "Behavior" -> "Site Pages" -> "All Content". Find that URL and click on it. Choose a secondary dimension of "Referral path" to see what is linking to it like that.
I suspect that you will find that you are linking to your home page like that from somewhere on your own site. If that is the case, fixing the link on your own site would be the easiest course of action.
You can also fix the problem using "URL Canonicalization". You can either use 301 redirects to remove parameters, or put meta canonical tags on your pages letting Google know what your preferred URLs are. Here is a guide to doing so. You don't say what software powers your blog, but there are plugins for canonical URLs for most blogging platforms. For example Yoast is a WordPress plugin that does it.