First and foremost, make sure he doesn't forego proper care. Make sure he heals correctly the first time instead of life long messed up collar bone and other possible issues related to this. It doesn't sound like it's life threatening (or he would have received further treatment in ER) but if it's actually displaced enough to require surgery, he could have significant issues down the road. If it comes to it, you can discharge medical debt in 7yrs through bankruptcy. Much harder to fix a shoulder, arm, nerve damage, etc.

Second, don't assume he can't qualify for Medicaid. I don't think private insurer will cover pre existing conditions, but double check. Many hospitals (especially non-profits) have payment plans or financial need assistance.