Cassette is finished...even if the chain wasn't worn, it was worn. That 11t is pretty worn, along with the next two cogs. But, based on the DruaAce lock ring, is that a DuraAce cassette? Maybe you can get away with just replacing the worn cogs, though, IMO, it's wiser and far less issue prone to simply start with a new chain on a new cassette...as per the general cycling wisdom handed down to us since Napoleon rode a bike to Moscow in 1812.