If you rephrased the proposition to "vanilla ice-cream tastes nice to me" it would leave you less vulnerable to skepticism.
When we use the words "vanilla ice cream is nice" most people are expressing the sentiment "I think that vanilla ice-cream is nice", though the words themselves don't make that clear.
Tastes nice" really denotes a binary relationship, a thing cannot taste nice independently, it requires a thing to do the tasting. Therefore that statement can only ever be true or false in relation to a perceiver of the taste.
Whether we can have objective knowledge of matters of taste is a contested subject in the field of aesthetics. David Hume suggests that it is, and puts forward a theory in Of the Standard of Taste that addresses the inconsistency in us stating that taste is entirely subjective yet still knowing deep down that Justin Bieber is an inferior musician to Bob Dylan. (Or any other musician in the history of civilisation).