I don't know which STD you are referring to, but in response to some other posters, the only way to prevent passing on an STD is through abstinence. Condoms are not 100% effective as you can transmit an infection through sores or cuts on areas not protected by the condom, in rare cases even through lice/scabies .
I assume you would have to prove that your partner knew they were infected. And also prove that they did not inform you they were infected (nigh on impossible, they could claim you consented and once infected, denied all knowledge). And it would also depend on the gravity of the situation, i.e. which type of STD it was - i.e. a curable bacterial one, or an incurable viral type.
Whatever you decide, take it as a lesson learned and next time choose your partner more wisely and get to know them well before sleeping with them.