'Flatten' satin sheen on wood stain
In general, it's the final layer that determines the amount of gloss in the finish. Adding another layer of matte should do it. 
However, another layer of stain will deepen the color. I presume from your wording that you are actually using an all in one stain and poly finish (minwax?)... That's the hazard with using those - everything needs the same number of coats. 
Alternatively, you could. Apply a layer of clear matte over the top. If sanding bothers you, you can also try steel wool, as it can be a little more forgiving. 

Ultimately, the best advice for finishing is always to test on scrap. You will likely not be able to match the gloss level of the current finish perfectly, and the aforementioned steel wool (0000 type) may help there.