Vomiting. Vomiting brings up acid from the stomach, this can irritate the esophagus--- which can cause esophagitis resulting in chest pain.
Couple of reasons. Chest pain induced by vomiting is unlikely to represent angina, though it is possible if the vomiting is an atypical presentation of heart attack. This can be seen occasionally. The esophagus can undergo significant strain during vomiting/retching, and it is even possible to tear it slightly, which can be dangerous if not immediately detected.