Chocolate won’t harden up on my cookies
The problem is the “small amount of oil”. If you measured wrong or just eyeballed it, you now have a chocolate spread instead of a solid coating.
Storing the cookies in the fridge may or may not be enough to solidify the chocolate coating, but apart from that, there’s nothing you can do to change the chocolate. Depending on what matches the cookie flavor, dipping the sticky part in something like grated coconut or ground almonds may at least protect your fingers somewhat.