I would make sure that your scouts know that they should report it. About your question for who can administer first aid, I believe anyone can. I don’t think there are age restrictions, I am the highest certified in my troop but I am a scout.
Boys, LOL, men are by nature not detail people. Sometime they, LOL, we will assume the best and basically ignore injuries. I'm looking at a few scouting scares on my fingers as I type through the arthritis. Usually, with something like this, the adult leadership comes up with kind of a policy for everyone to note. Doesn't have to be a written policy, but a mental process that if an injury has bleeding or protruding bone, the responsible adult needs to be told so they can determine what, if anything, needs attention. I would make it a troop policy for everyone, not just the scouts.
@CarlosD welcome back from your first time as "the guy!"
1. Don't beat yourself up about this. Trust me, it could be worse. Thank the parents for keeping you in the loop about it. And, yes, let the camp director and your district executive know. Sometimes when a scout does something like this, it is exactly as the scout described. But sometimes, it might have involved more scouts either purposely or by accident. The only way you'll know is to ask broader questions. And the only way you can do that across all the other troops who've been to camp is to let them know. If yours is the only report, it will get filed and be just one more statistic. But if there's a second one like it from the same week they might catch on to it and avert a larger problem.
2. We had a different situation, but same indirect reporting. So ... in addition to addressing the primary issue, we committed some time at a subsequent meeting having a scoutmaster conference with each scout. It basically went, "We just wanted to let you know, that you guys can trust us. You can let us know if something isn't going right. And if we need to deal with it, we won't make a big scene and single you or your buddies out."
That got us some constructive feedback ... especially from some scouts who thought their buddy was going to let us know about the situation. Those scouts learned about communication gaps, and the others seemed to be a bit more responsive in keeping us in the loop.