Have you let them know what's happened, and what was their reaction?
Because I have 3 dc whose reaction would be totally different. One would have been telling them she was in agony, couldn't cope etc. I'd have had a phone call telling me to go to A&E. The other two would have said they were fine, insisted they were fine, even if they'd even gone to medical in the first place. I've spent many an hour sitting in A&E with the first to be told all was well, not to worry. With the other two if they admit something is a little painful, I start packing bags to go.
With one of the latter two, for example, he came out of school a couple of years ago and I knew from across the car park I was off to A&E from the way he was holding his arm. He'd done it in football. He was insistent it was fine and perhaps an elasticated bandage would make it totally fine.
After some negotiation, eventually he agreed to go to A&E and yes, as I was fairly confident, it was broken.
To cut a long story short I had an apologetic email and telephone call by 9:30am the next morning. He'd told the teacher it wasn't really painful at all, showed them he could do all the movements etc and they were horrified to find that wasn't the case.
I did tell them that he will avoid medical at all costs and nearly didn't have his (very necessary) appendicectomy due to rating it 2/10 on the pain chart, so not to believe him when he says it doesn't hurt!
Even with that knowledge he's come home with a 2" gash due to a stud in the arm-which he'd carefully hid from teachers for most of a day at school. (He was most put out when I told him it needed washing. Apparently it was "clean mud")
So what I'm saying is it does depend on their reaction when they find out that it was more of an issue.
I didn't blame school at all for not spotting as I know he will play it down and hide it. However their reaction when they found out was important. If they had played it down and shrugged "oh well" I would have been much more concerned.