This will vary from state to state, but most states will have a statute of limitations on personal injury cases.
In other words, you will have a limited amount of time from the date of your accident to file a lawsuit against the responsible party.
For most states that window is two years.
Failure to file a claim within the statute of limitations means you lose your right to be compensated for your damages.
Knowing that, it's important to contact an attorney as soon as possible so you can get started on your claim.
It's in your best interest to be proactive and file a claim with an attorney as soon as possible.
The sooner your attorney gets started on the case, the better chance they have of preserving evidence and mounting a successful claim.