This symptoms is very unlikely to be a sign of anything serious going on with you heart. it probably is some form of musculoskeletal chest pain. Regardless, I would still encourage you to stop smoking and try to lose some weight. Those two have a tremendous impact on your health in the long run and will do more good than anything any doctor or medication could.
At the risk of sounding like a preacher on his soapbox, I have to say that even less than 10 cigarettes a day is still too many. One cigarette a day is one too many. Each cigarette will cause blood pressure to rise and the chemicals do all kinds of damage to your body, including lowering oxygen concentration in the blood. I smoked heavily for 20 years and stopped in Feb 2007 due to a heart attack. In Sept last year I had to have a very risky angioplasty procedure on my heart and was admitted to Imperial College London. I was scared stiff and sneaked outside to have a cigarette to calm my nerves, or so I thought. I managed to get a cigarette off another patient, lit it, and took one puff. Sheesh, I wish I hadn't. I couldn't stand up for 10 mins, I thought I was going to pass out. I managed to get back to the ward and I admitted my naughty behaviour to the nurse. When she took my blood pressure it was 160/110. I had to lay flat for over an hour for it to settle down. This is how cigarettes really affect your body but yours is healthy enough to counteract the effects, at the moment. My surgery had to be delayed which made my Cardiologist very angry, but I did learn a valuable lesson and got the truth I needed. I had lived in denial for years saying how cigarettes are blamed for everything and they don't do much harm. I thought it was all exaggerated until that moment, but believe me it's all very true.
I know it''s hard to quite, but it really is worth it long term. I can vouch for that having had a triple bypass and 6 stents, all due to those poison sticks:(