Have Burning Sensation Along Arm To Chest. No Sign Of Heart Attack. Allergic To Aspirin. Recommendations?

My husband is having burning sensation all the way down his left arm, in the shoulder and on the left side of his chest.
He went to the er last August for fear of having a heart attack. No sign of a heart attack with blood work and ekg or eeg, don't know which one or both were performed.
The pain is not sharp or sudden, but constant. The pain intensity does change. He feels pain when he touches his shoulder, wearing the seatbelt hurts. It does not hurt to the touch on his chest or on his arm. It does not bother him when he lays down. It starts to hurt about 5 minutes after he gets up in the morning.
He is allergic to aspirin, so taking that as a blood thinner is not an option.
He feels relief when he puts his hand in his pocket instead of letting it hang.
I was going to have him put it in a sling and wear this for a couple of hours to see if that would help.
We are concerned that it is a cardiac event, but it does not sound like it. Help?