Accidentally dragged Excel icon into Preview icon on dock

Hello community.

This is my first post here because I never have problems with my mac products. 🙂

I've recently acquired a later model Macbook Air 11 inch. I have updated it to OS X Yosemite.

I was changing the dock around and I accidentally dragged Microsoft Excel from my Applications into the Preview Icon on the dock (it was meant to go next to it on the dock).

Now, every time I right click Preview on the dock, the Microsoft Excel icon is there and when I right or left click it, about 1000 blank pages open up. I believe preview is trying to open excel.

I can ignore it, but the OCD inside me won't let it go and I would greatly appreciate any help

Thank you