If thats the pump at the front you can service it from the front engine cover. What can happen is that the water pump gets hit, that can bend the front cover and water pump. This can break the shaft from the oil pump to the water pump and the drive chain can come off. This will cause the oil light to come on. If you are lucky it's the oil pump drive chain making the clicking noise and not something more serious, this would depend on how long you rode it for after the light came on. To fix this you would need, front cover, water pump, oil pump, drive chain, cover gasket and O rings. You will have to remove the clutch basket to put the chain back on as well. First thing to do is check the water pump for damage and take it from there.