What Causes Severe Pain In Chest And Shoulder?

Hi Doctor, I was a heavy smoker until 4 days ago, when I had severe pain in the left side of my chest and left shoulder, the pain increased with inhalation. I thought in the beginning that I am getting a heart attack. I stopped smoking totally. The pain is much less now, but still present. should I still see a doctor? I am 38, never had heart problems, even my heart beat is normally slower than average arouund 50 pulses

/min. thanks