I had sex once with one partner. the next day i had sex once with another partner. that same week, that first partner told me she had chlamydia. should i worry that the second partner may have it?

Sure: Chlamydia is a common sexually transmitted infection. Unless a couple is monogamous (no current partners outside the couple) and are sure they both do not carry chlamydia germs, then a person should always worry that others may have it. Sexually active persons can get screened by a urine test (looks for chlamydia, gonorrhea, trichomonas) as part of their annual check-up even if having no symptoms.