Find the mouse, first.
You are going to have to find that mouse and get it out of there, then thoroughly clean the area. Regular air fresheners won't do the trick. Products like Febreze and Oust do...
Get rid of the mouse and bleach or clean where the mouse died. If the mouse is in a wall or other inaccessible place, you'll have to wait a few weeks for it to dry out before the smell completely...
Well, Id use some candles or air freshiner. Niether does it make the smell go away but it makes your house smell really good!Open the wall and get rid of the mouse. It will get worse before it gets...