Throbbing pain in the armpit may be a result of injury, inflammation, pulled muscles and pinched nerves. Swollen lymph nodes may also cause pain in the armpit, according to WebMd.
In most cases, pain in the armpit diminishes on its own. However, it sometimes may be a sign of a more serious condition, such as a cyst or a tumor. Cold compresses and over the counter medication may speed up the recovery. If the throbbing pain persists or if the patient notices a growth, seeing a doctor is advisable. Underarm pain that feels like pressure may be a sign of an underlying heart condition, according to Healthgrades.