The lungs are not getting rid of the CO2 enough. The body can also remove the C02 by breaking it down to carbonic acid by the enzyme carbonic anhydrase. They are responsible for removing the acid and producing bicarbonate which neutralizes acid.
Acidosis can be what causes the chest pain.
Treatment for this may use brochodilator or steroid inhaled drugs. Excercise of any sort is good. Moving the arms up and down 10 times each will get the blood circulating. Try to walk a few steps. When the body moves the enzymes start to work better again.