28wks preg ob did internal exam as had vag spotting. was uncomfy,cervx was closed/firm.can repeat internal cause harm had pinkish discharg12hrs later?

Highly unlikely: While an exam can cause some bleeding if your cervix is raw/friable, it will not cause harm to your pregnancy at 28 weeks. It is important that the exam be done and sometimes repeated in order to know if the is a problem that must be treated so the pregnancy can continue without problems. Sometimes this will cause some spotting but it is necessary. Best wishes.