It's usually okay to walk on a sprained foot as long as you take it easy but if you notice any pain when walking on the sprained foot then you should cease walking and rest as much as possible until the sprained foot heals.
Walking on the sprained foot could make it worse if the sprained foot is more serious.
You should use some crutches or a wheelchair to get around if needed to avoid hurting your sprained foot any further.
It's best to avoid walking on the sprained foot for at least a couple days and then return to walking slowly and easy until it heals.
If any sharp pain is noticed when walking on the sprained foot then stop until it heals.