Did you convert traditional to roth or did you recharacterize you 2017 traditional contribution to roth? I know it sounds like the same thing, but it's not.
If you recharacterized, that's basically like making it as if you had contributed to to the roth in the first place, which is what you want since the traditional contribution is not deductible. This assumes you're under the roth income limits, which you should be if you were previously eligible for traditional deduction, unless your income went up ALOT. You'll need to attach a statement to your return explaining what you did.
If you actually converted traditional to roth, that would be a taxable event. I think you should be able to recharacterize the conversion back to traditional (this is the last year you can do that as the new tax bill ended it after the 2017 tax year) and then recharacterize the traditional contribution to roth (you'll continue to be able to do that as conversions won't be able to be recharacterized, but contributions will).