I had major surgery on my feet in Feb and have consequently suffered fallen arches and awaiting orthotics to be made.
The exercises I have been given are:
place a piece of newspaper on the floor, and scrunch up the paper by pulling your toes towards you...
with your foot out in front of you, move the top of your foot to the left and hold... and repeat
then same to the right...
You would be wise to visit a doctor tho to get medical advice if the pain is bothering you. You can buy basic orthotics to support the arch from most pharmacies.
Wishing you the best of luck.