Can you Know something and not be right about it?
Accepting, for a moment, that 'knowledge' = 'memory' (without the arbitrary egoic value judgements of 'right' and 'wrong'), I say 'yes', memory need not be 'right', nor 'knowledge'. It is all 'correct' for you (momentary perspective).
For there to be knowlege, there must be rightness (objective truth).
Nope, see my definition above, of 'knowledge'. It is a very supportable definition, by evidence, logic, etc.. So, from 'this' perspective, two perspectives can be diametrically 'oppositional' and both remain 'correct' (to one extent or another) for the observing Perspective.
If you concede that our memories are not connected to objective truth
No need to obfuscate the discussion with such 'meaningless' terms as "objective truth'..
(that we each just have our own interpretation) then you are also conceding that knowledge doesn't exist.
"Everything exists. Existence is contextual. Everything exists in its context." -Book of Fudd
Unless you define knowledge subjectively.
All definitions are subjective. Definitions exist solely as a product of individual 'thoughts'/concepts.
We each just know what we know
I pay no serious attention (do not 'believe'), as 'memory/knowledge is different from moment to moment. What I 'knew' one day, I 'know' differently today, a new perspective, new memories...
but our knowledge doesn't say anything about the world objectively.
What gives you the impression that there is a world beyond your nose? There has never been evidence (nor can there be) of any 'out there world'. Nor is the concept of 'objectivity' meaningful, as it is by subjective thought alone that you can even think about it.
Your 'knowledge' says much about YOUR world, at the moment of observation. And no one can say that is 'false' or 'wrong', for that is your true experience and knowledge. Every Perspective is unique! And as so, 'correct' (even 'right') for you. Sometimes other perspectives see things similarly (and off they go to form a society) and many don't. Not 'right' not 'wrong' just different.