If nitro gets rid of chest pressure should medical care still be sought?

Depends: Angina, relieved by nitro, can be a symptom of stable coronary artery disease if the pattern of pain (what causes it, how quickly it fades, how often you get it) is unchanging. Stable disease can be managed at home. Any change, particularly new angina at rest when it used to be only with activity, or if you are awakened, should prompt a call to your doctor or a trip to the emergency room.

Yes: Especially if first time, or if getting worse (more intense and/or more frequent).