1) If someone is at fault in causing an accident, you may sue them for damages, including medical costs. The fact that they do not have insurance, or insurance for that type of loss or injury, does not mean they can't be sued--it just means that there is no insurance to pay any judgment, and if you win, you have to collect directly from the defendant. This can be problematic in the event of defendants with low income and few assets. The critical issue is fault--you can only recover in a lawsuit if the other party was at fault, such as being unreasonably careless.2) A reasonable settlement would be: a) your out-of-pocket or unreimbursed medical bills, both current and projected future (e.g. if there is going to be follow-up, additional surgery, physical therapy, etc.; and b) in the event of lingering loss of strength or function, or lingering scars, some amount for pain and suffering. Valuing pain and suffering is an art, not a science; if ultimately your son will recover fully, but has experienced some weeks or months of weakness and pain, plus will have some scaring, a reasonable amount might be equal to your out-of-pocket medical bills.However, be prepared to accept less if you can get it quickly, without the cost and time of litigation.Ideally, since valuing recovery for injuries like this is so difficult, you should consult with a personal injury attorney to see what you and your son might be entitled  to.  Good luck.