If I failed to include IRA basis year-after-year (on Form 8606, line 2) but made regular nondeductible IRA contributions, should I simply correct it in my 2019 return?

I have failed to include info on previous years, but have made no withdrawals and I do not believe this missing info has had any impact on my tax return.

2nd question: when calculating tax basis for nondeductible IRAs, does one also need to include the cost for reinvested dividends/gains?

Thank you!