Missy, I'm not a doctor, so do not rely on what I (or anyone else here says) to make a decision about whether or not you are having a medical emergency. Chest tightness is nothing to treat casually.
That said, check and see if it's really a symptom of anxiety, not something more serious. Try this: Take a very deep breath, hold it for the count of three, then exhale gradually through tightly pursed lips. It should take you 20-30 seconds to exhale this way. Repeat 1-2 more times.
Then, just breath normally, and see how you feel. Is your chest still tight? Do you feel less anxious breathing? If so, it's likely you're having an anxiety response. In that case, what you need is A DISTRACTION!