Why do i get a slight pain in my foot arch when i stop running?

It could : Be strained and while running you are unaware. Ice the arch, try a arch support while you run. If you already have one make sure it's a proper fit.

Plantar fascia: Strain of the arch or plantar fascia may have occurred. Pain can be treated with ice but you may need to see a foot specialist for a biomechanical evaluation and orthotics.