Ask the Attorney: How late is too late to file a claim?

Ask the Atty,

My daughter was involved in an accident on the highway last week and the traffic was so bad that all they did was exchange information, she then pulled over at the next exit.
It turns out that she banged her head in the accident and suffered a concussion that was confirmed by our doctor on Friday. Can we still file a claim even thought here is no police report?
It will be expensive for continuing health care, car damage, and missing work!

Caroline M