Probably muscle. Could be muscle or joint or bone related. Sometimes gall bladder disease can cause referred pain.
That depends. The description of the pain suggests the cause. The word constricting or pressure or tightness are suggestive of a block in the artery that could lead to a heart attack. However, on the right side of the chest is less likely to be for that reason, more likely if in middle or left chest. There are many other reasons for chest pain and tests are sometimes needed to be sure of the cause.