Icy sidewalks under a thin layer of snow are, to say the least, treacherous. At some point all of us take a fall. It may take the form of windmilling arms or a quick thunk on the back side. Your body and the ground make a hard collision.
Stiffness and bruising are usually the result. They are painful but typically resolve on their own within a few days.
If pain persists beyond a few days, it is advisable to seek medical help. Many a bruise covers deeper injury such as a chipped tail bone or a small fracture. Pain that lasts and doesn’t get better can be a sign that help is required for full recovery.
Wishing you a safe winter!