could be the relay that powers the lights, also there is a few other fuses that also feed the headlight switch with power that may have blown so its not triggering the relay etc.
may also be a dodgy wire anywhere in the system too.
basically try the simple stuff 1st like swapping the relay out for a similar one nearby & see if the problem sorts itself, if it does buy a new relay & your sorted, if not move onto the next thing ( fuses ( all of em ) & switch etc )
then after that its a long drawn out task of testing each stage of the system with a multimeter or similar testing device ( a couple of bits of wire attached to a working bulb will do inplace of proper testing gear if you dont have a multimeter :L )
may also be a dodgy wire anywhere in the system too.
basically try the simple stuff 1st like swapping the relay out for a similar one nearby & see if the problem sorts itself, if it does buy a new relay & your sorted, if not move onto the next thing ( fuses ( all of em ) & switch etc )
then after that its a long drawn out task of testing each stage of the system with a multimeter or similar testing device ( a couple of bits of wire attached to a working bulb will do inplace of proper testing gear if you dont have a multimeter :L )