Got coldsore first time in my life. mouth ulcer and sore back of throat. also slight pain in lower esophagus. will it go on its own? been 9 days

See your doctor: The combination of sore throat and pain behind the sternum (especially if burning pain) are possible signs of acid reflux disease with LPR (laryngeal-pharyngeal reflux). However, sometimes symptoms are not caused by the same problem ("esophageal pain" could be from coronary artery disease). Seeking attention from a doctor who knows you well is important, especially when symptoms don't go away.