Could it be heartburn?
If you are a female, sometimes what feels like heart burn can turn out to be a heart attack, so if you are having persistent burning that feels like heart burn but doesn't go away with anti-acid, please call 9-11 or have someone take you to the nearest hospital.
If it is an external burning sensation of the skin, have you looked to see if there is any abnormal appearance of the skin? With the hot weather, might you be having some chafing going on along with the trapped sweat bacteria?
If it feels like it is just beneath the surface, you should get it checked to make sure it is not a blood clot causing the burning sensation (don't massage area).
I went through a period of time when (usually in the shower) I would touch a certain area near by breast and the discomfort was awful. It was rather like the sensation I got after breaking my left leg, following surgery. It FELT like a match had been lit and then thrown on my foot. That's what I was feeling with my breast, so I knew that some nerves (somewhere) had gone all wonky! I gave it some time and eventually everything went back to normal when the pressure on the nerves subsided. I'm not saying that is what is happening to you but it's a possibility. If the pain continues then I would suggest you see your doctor. I send you my best wishes! Take care ..