Fitting new headlight blew something and engine stopped running

Hello, I was fitting a headlight to my car and decided to run the engine while testing the light. I should say at this point that the engine has never failed to start and has run perfectly up to this point. I switched on the sidelights and all was ok, then when I switched on the dipped beam, there was a faint pop noise from somewhere and the engine stopped. The engine will not start now although it cranks happily. Ironically, the headlight works fine but something happened to the engine electrics when I switched on the dipped beam. Does anyone know what math have happened please? I’ve checked all fuses and they’re ok. There are no dash warnings.

Thank you, Stephen