If you are looking for rehab, you should get therabands and do dorsiflexion, plantarflexion, inversion, and eversion. Wrap the theraband around your foot and move it up, down, inward, and outward twice a day and building up slowly to a decent amount of reps. You want to build up strength around the ankles so they can support you from collapsing inward as the weight of your body is trying to be supported by your foot.
I would also work on inner/outer hip strength as well as plantar strength. You can do a variety of hip exercises (fire hydrants, side-laying leg raises, etc. ). Sometimes having weak adductors (inner hips) can cause the collapse instead. Always work on your abbductors (outer hips) if you work on the inside to avoid muscle imbalance.
Your plantar you can strengthen with tower crunches. Also, you can practice raising your big toes up (while keeping the rest of your toes planted on the ground) and then vice-versa. Again, as you strengthen and rehab one are of the body you also want to strengthen connected problem areas to avoid potential future issues coming from imbalances.
In the meantime either A) STOP RUNNING or B) GET SOME KIND OF OVER THE COUNTER/CUSTOM INSOLE TO HELP RELIEVE THE PAIN. Do not get in the habit of relying on this. It will only create further muscle imbalances in the long term. For the time being you must calm down the pain to do proper rehab. If the insole don't work then you really should just stop.