If you already filed your return without the 1099-R, then you should amend your taxes to include the form even if it doesn't affect the outcome of your refund/payment. The IRS matches forms they receive with forms that you report. 

But wait until the original return is fully processed. If you had a refund/tax payment due wait until you receive the refund or the payment is processed. After the original return is fully processed, select the link below for amending instructions.

In the meantime, make no changes to your original return. This can really mess things up. 

https://ttlc.intuit.com/questions/1894381-how-to-amend-change-or-correct-a-return-you-already-filed