it might be that the toy sword has caused a small bleeding the eye which is seen as the dark spot. if the spot is not increasing and if your vision otherwise is fine, then maybe there is no need to see a eye specialist.
u may consult a doctor if -
1. your central vision goes down
2. you see multiple 100's dark spots in front of your eyes
3. if a significant part of your peripheral vision
mild pain after trauma is ok. u can take any mild OTC painkiller for the same.
get well soon