Of course you administer oxygen. A pulse ox of 95%, while low normal, in the presence of classic cardiac pain (angina) is clear reason to use oxygen. Angina is reduced blood flow to the cardiac muscle, producing intense pain as described. Administering oxygen and saturating the oxygen carrying capacity of the blood will make more oxygen available to oxygen deprived myocardium.
In fact, if the chest pain improves or disappears solely from the administration of oxygen, it is a very strong indicator that the cause is cardio/respiratory in origin. DO NOT BE STINGY in administering oxygen. It is unlikely that too much can cause harm, but very likely that too little will not be effective. Use a high flow mask and monitor vital signs and 02 saturation.