Small touch up FUE to missed spot on temples?

There is a risk, most certainly. That does not mean it can't be done, but it is not as simple as first glance. There of damaging the existing hairs that were there initially. They have had some trauma with the surgery and this is more trauma/injury. There is a risk of damaging the new grafts.  They have been working hard to survive and the effect of further injury right now is somewhat unknownTheir is a risk of poor growth as grafts are going into skin that is now in healing phase (there is inflammation there)There is a risk of asymmetry if things are a tiny bit swollen, it may be hard to know precisely where to place the graftsEverything has risk. The decision on whether to proceed or wait comes down to understanding the risks and benefits

You can do a touch up FUE after a week.  You do not need to wait weeks if its just a few grafts that need to be implanted.