If the adjuster's offer is too low, you will need to file a lawsuit for negligence against the party who caused your injury.  It is possible that as the case proceeds through litigation that it may or may not settle for a larger amount prior to trial.  Another option other than trial is arbitration where an arbitrator might or might not award you a larger amount than the present offer.  You will need to file your lawsuit prior to the expiration of the statute of limitations, otherwise you will lose your rights forever in the matter.  It would be advisable to speak with a personal injury attorney.  Another factor to consider is if through further negotiation, the difference between the amount you are seeking and the amount offered by the adjuster is a sufficient difference to warrant litigating the matter.