Hola Dee

Garillo is a word in the world of vineyards and it refers to a device (a type of sickle) used in the process of collecting grapes. I also struggled to find it in the dictionary (I imagine it is an old word/item that doesn't seem to be used any more, and it's disappearing) 

Here's an entry if you want a full description of "garillo" that I found.

"Me voy a llevar la mano con el garillo" means "I'm going to cut my hand with the sickle".  It conveys some sort of damage to the part of the body you are referring to.

I hope it clarified it.

Saludos

Inma