hi , direct contact with cold
air and air conditioner always affects the chest muscles. if one is close to air conditioner on front side chest towards the coming cold air, then there chest muscles are affected and it pains. sternum
is the weak bone and is easily broken in a slight blow as well. but you can manage this pain by adopting few life styles like avoiding excessive use of AC, no close setting with air conditioner and windows. application of local pain relief gel , and in severe cases some analgesics and muscle relaxant
can help. regards.