Very sore left heel after a spinning session. specially when i bend down and stretch or pull my foot upwards.

Plantar Fasciitis: It sounds like acute plantar fasciitis. It can occur with exercise, especially if it's a new endeavor. It can also happen with repeated stress to the foot over a long period. The thick and fibrous plantar fascia gets stressed and strained, causing inflammation and pain. Rest, ice, massage, and anti-inflammatory medicine are good starts. See a doctor if it continues for more than a week.