You do not need to amend your 2017 tax return as your settlement was received in 2018. This should be reported on your 2018 tax return.
Generally, any portion of the settlement that is not used to cover your medical expenses for treatment of physical injury or emotional distress, is taxable. It would be smart to make an estimated tax payment for this income. The payment due date for the first quarter is April 17, 2018.
