Hi. Since you have the pain when you lie down it is less likely to be due to any serious heart problem. The
pain could be because of gastric acid reflux. Muscle pain could also be a possibility. Other likely causes
could be a problem in lung or some of the organs of digestive system. Watch out for other symptoms indicating
the heart such as- heavy pressure like feeling in chest, sweating, pain remaining for short duration and
getting relieved after a time. You can take any over the counter antacid and painkiller to see if these help.
Otherwise please do not ignore and get yourself examined to rule out any heart related or other significant
problem. Hope that helps. Take care.