How advantageous is it to have presented a poster at an international conference?
It's probably best to listen to your supervisor, especially if they have seen your data. If they have not, show him/her your work and explain to them why you believe this conference would benefit from you presenting. That way you have greater clarity regarding why they disagree, and you frame it as the conference benefiting from your contribution rather than you simply gaining a reputation advantage by presenting premature data.