Mild chest pain. what kind or degree of chest pain is something to worry about?

Not severity: Severity is all but irrelevant as heart attacks can be painless. The single most important feature of angina is that it is provoked by exercise and relieved by rest. That said, a heart attack can come on at complete rest (and often does). If you're concerned, please see your doctor. An once of prevention is worth a pound of cure.

Varies: Anginal symptoms are unique to every individual. Most people undergoing an acute coronary syndrome experience an opressive sensation in the chest, not necessarily pain, specially on patients with diabetes. Any chest pain is of concern and should be evaluated by a cardiologist. Sometimes the most lifethreatening coronary stenoses produce no pain, just sudden death, like a critical left main.