As the accident was only a couple of days ago it is a short time to get over it, it would have been upsetting to see his mom's leg cut and hear her pain. after reassuring him it is always best to ;let it go , sometimes if the matter is a constant talking point children become more afraid , so make sure it has run its course of conversation, if he asks just say Mommies leg is all better now .When its windy make no issue of it ..this was so short a time ago .it will pass ...