What Causes Stinging Sensation In Shoulders And Back After Having An Heart Attack?

Hi my 49 yr old husband had an heart attack 22 wks ago, he as been doing very well, he does exercises every day, but the last few days he s having stinging pain in his shoulder blade then it s went to the top of is back, and now it s in his chest both sides. There is nothing on his skin but sore to touch.Hope you can help,Louise