Originally posted by PawnokeyholeSic should be used with square brackets and italics.
Not to mention he forgot the Oxford comma after "war mongers" (sic).
You should only use it after an error in something you are quoting to show that the error was in the original and was not made by you. You should have posted his entire quote if you wanted to use sic and it should be left inside the quotes.
e.g. "Not to mention he forgot the Oxford comma after 'war mongers' (sic) [sic]."