Ideally all three go together but if the sprockets aren't worn too much, it could be okay. If you've put more than a couple thousand miles on I would seriously consider new sprockets. Depends how the teeth look. Regardless the stock chain, if that's what you had, is not very good and so may have given up early, leaving the stock sprockets relatively intact. Putting a new chain on worn sprockets is likely going to result in premature chain wear.