Yes you should prepare an amendment for your 2015 and 2016 returns as the IRS expects taxpayers to report all income-unless your interest was below $.50.

However, when you amend, if the result does not make a difference, you can disregard it.

If the result does change, print and mail the amendment (it cannot be e-filed) and allow about 16 weeks for processing.

See How Do I Amend a Return Already Filed?

Do claim your interest income for 2017 if it is over $.50.