Are toddlers scared of the dark? My 18 month old sleeps alone in his room. Should I be leaving the light on?

i have this issue with my first kid. We off all the lights when we sleep last time, childcare he is not able to nap due to abit of light beaming into the area where they nap . so after that i on the toilet lights in order to let him get use to not so dark area. now , he is too afraid of dark ! sometimes i really scratch head dont know what to do