sexually transmitted infection is transmitted by unprotected sexual activity. signs and symptoms of STI in men vary depending on the type of disease some may have pain in urinating (which can also be present in patients with UTI or ureterolithiasis), penile discharge, low grade fever, swollen testicles, blisters on the skin (penile, testicles, around the anus), tingling, itching or burning sensation around the blister, genital warts or warts around the mouth (for people who engage in oral sex), headache, sore throat and swollen lymph nodes. have a visit with your internist for further work-up and antibiotic treatment if indicated.