The lightbulb in our bathroom made a loud bang & turned off a few days ago. We took down the bit covering the light bulb to change bulb & it stunk of fish! We have just left it with no bulb in but the smell is still there. We think the bulb wattage was too high, can we just replace it with a lower wattage bulb or do we need to get it checked out in case any part of the light/ wires etc are damaged?

The lighting fixture should have a label on the outside of the bulb socket that gives you the maximum wattage bulb that can be used. Did you exceed that wattage?

However, I would be more concerned that the conductors going to the fixture got to hot and started to melt or char. That needs to be checked by removing taking the light fixture down and looking at the conductors. You do not have to disconnect the wiring, just look for evidence of damage.

I have heard that sometimes the light bulb if it is over heating will cause the light bulb socket to get hot which in turn will cause the adhesive on the label (if there is a label on the outside of the socket) to release an odious smell.