K-Meta and Campden tablet are two different ways of adding sulfite to a wine/mead/must/etc. Sulfite stops bacteria and oxidation, so it helps keep the wine/mead/whatever from going bad. However, bacteria are unlikely to be a problem at this point, and oxidation is, unlike with wine, rarely a problem with mead, so you'll probably be fine as it is. I personally never add any sort of chemical additives to anything I make, and I never have any problems.
That said, you could certainly siphon what's left to a bottle if you wanted to, assuming that the bottle is well sanitized and assuming you haven't made the 1 gallon container all dirty by drinking out of it directly or something like that.