Ask an orthopedic surgeon for advice.
The pain at your rearfoot needs to be thoroughly evaluated, because there are many causes. Under the body's weight, the plantar arch tends to get depressed and can wear the tendons (posterior tibial or peroneal tendinopathy) and the joints (sub-talar arthrosis). Tendon cleaning (synovectomy) or more complex repairs (tendon graft or tendon transfer) may sometimes need to be performed.
When flat foot or pronounced arch deformaty is too severe (planovalgus or cavovarus foot), bone realignment (osteotomy) or a partial fusion of the rearfoot (sub-talar arthrodesis) may be needed.