My wife was in a car accident several months ago and a couple of our children were in the car with her.  One of them (who happens to be two years old) saw a doctor and our insurance agency has been wanting us to do a settlement for $500 (we think he's likely fine)..  I am unfamiliar with the ins and outs of this - my concern is that if I accept the settlement and later it turns out that he IS hurt in some way (maybe a chronic condition) that he is unable to communicate to us we will have no recourse. My other concern is that if we don't accept the settlement, that we won't be able to approach them later if he does have some injury (I do not know if there is a time limit for claiming bodily injury after an accident).

Could someone please clear up my concerns:
  If we accept the settlement and later incur medical expenses due to some condition that we didn't know about, will we be out of luck?
  If we don't accept the settlement, is there a time limit on how long we have to file a claim for those medical expenses?

We already have filed a claim (to pay for the doctor visit after the accident), which is why they want us to settle..