Dash bulb warning light on but no bulbs out..?

I recently installed a new bulb housing behind the left taillight assembly as the original was not making a good earth on the reverse tail light. Works fine - but a day or so later I notice the dash bulb warning light on but no bulbs out..?

I checked all my front and rear lights and they work.

I do notice when I turn the my lights from ON to parked there is a click coming from the fuse box - not sure if that is connected to the bulb warning light being on..?

Any ideas?

Maybe just I should remove the housing at the rear and check the bulbs are all making good contact..?

Dean