Rest, Ice, Ibuprofen and Silly Putty.
No joke, Silly Putty could work well if you can wrap it up in such a way that it doesn't squish completely out from under your heel during use.
Put a bit of silly putty under our footbed/heel. Make sure to wrap it tight in something (duct tape maybe) though so it doesn't stick to your liner or just get squeezed out the way.
Silly Putty is about half PBDMS which is the active component used in dilatant armour and padding (e.g. D30's stuff for sports, Liquid Armour for military/ballistic protection).
It soft and flexible until it gets hit upon which it turns hard and can absorb an amazing amount of energy.