Collapsed Arch on Right Foot Hampered by Arthritis

Collapsed arch on right foot hampered by arthritis

I have pain on the sole of my right foot that has been brought about by using restrictive footwear in a warehouse for 10 years. Flat foot has meant the arch on the left hand side of right foot has been painful but mitigated slightly via exercises suggested on here pushing the toes back towards the leg cross-legged and pushing the foot against a tennis ball to strengthen the arch. Does anyone have any other ideas that can mitigate the pain whilst I'm at work? Have to go back and work in pain over the next week.