Pain back of left ankle & under heel to arch. swollen ankle only. xray show arthritis. no sign of fracture. no bruise. color good. cant bear weight.

Insertional achilles: Insertional achilles tendonitis and calcinosis. Use a heel lift in shoes, do not walk bare foot, use any form of mentholate gel ie: biofreeze 2-3 x daily. Possible use of anti-inflammatory if you are cleared by your doctor.

Possible : Plantar fascitis though it doesn't effect the back of the heel. Back of heel would be achilles i suggest MRI at this point if nothing is on x-ray.