A risk assessment is a pointless thing. I was taught how to write one when I trained to be a teacher and very swiftly realised that it had nothing whatsoever to do with keeping your pupils safe and everything to do with covering your backside, should anything untoward happen at any point. I got marked down in a lesson observation once for failing to point out that there was a risk of pupils stabbing themselves in the eye with their pencils. Now, I've taught some kids who have done some pretty stupid things in class before, but poking pencils in their eyes is not one of them. Poking their fingers down their throats to see how far they could get them down there before vomiting* - now that's something I've dealt with. Emptying the contents of a pencil sharpener into someone's ear - I've dealt with that too ("Quick, turn your head on one side and give it a bash with your Numeracy book."). Not pencils in eyes though.
The thing I've come to realise over years of working in schools and a couple of years at home with a small child is that you can never be fully aware of all the risks. You childproof everything only to find them scaling the curtains one day. You remove all small and pointy objects from a grab-able height only to discover them under the computer desk clutching a dismantled ball point pen, a biro spring protruding from one nostril.
My technique these days is to worry about the big stuff - heights, poisonous things, road safety - all that jazz. I don't panic about the little things. Rory got hold of a box of cocktail sticks earlier. I continued to check my emails and let him get on with it in a "Meh, he'll be fine. He's not stupid enough to impale himself on one of them" sort of way. And he wasn't. He did, however, create a lovely scale model of a porcupine by sticking them all in a nice fresh turd in his potty. Assess the risk of that, OFSTED.
*not very far, apparently.