What should i do if it occurs to me that, i have probably made mistake in the previous salah?

I was just performing Isha, and while on the Witr it occured to me that, I've probably skipped the second rakah on the Sunnah? Because I couldn't remember what surah I recited on the second rakah of sunnah. So should I restart from the sunnah? What if I did perform the salah accordingly, just couldn't remember and from doubt I performed again? Will both be accepted?