My husband is having a pain in the left side of his chest.?

He works on in the hot sun all day long. He dose not have any pain in his arms. It began hurting about two days ago, the night before we were wrestling but he had no problems till the next morning could that be the cause of it. He says the pain is constant and increases when he bends to either side. He does smoke but eats healthy. I told him that I could be indigestion but I am not really sure. He is only 22yrs. old also. Could it be a heart attack or something to do with his lungs? Also, he experienced a shortness of breath for about a minute.