Unfortunately, there is no spray you can use that won't damage the pachy as well. Herbicides are not smart enough to know the difference between a weed and a more desired plant like the groundcover :-)

You will have to manually remove the weeds. But that will give you the opportunity to loosen the soil a bit around the existing groundcover and apply a light granular fertilizer. That should help with their density and encourage the spread. You can transplant a couple of rooted starts from other areas to the bare spot or just purchase a couple of new starts to fill in, if that is easier.

Once you have the area cleaned out of weeds, you can apply a pre-emergent weed control like Preen. This will have no effect on the pachy (or any existing weeds so they must be removed) but will prevent new weed seeds germinating and growing. A good layer of mulch will do the same thing but mulch is often hard to apply well to an existing patch of groundcover.

This system works best for me,

see https://theherbladyblog.wordpress.com/?s=how+i+control+weeds