my lighter fell into the hole at the handbrake and I cannot see it in order to remove it, will this cause any damage if I drive the car?
Probably not, most likely it will find some cavity and remain there for the life of the vehicle. However it is full of fuel, if it were get close to a heat source the results could be bad.
Often handbrake covers are removable, it depends on the car how much work it would be. You could try and use a magnetic pick-up tool to retrieve it as well.