I developed several knots in both armpits after five weeks when for some reason intense chest and back pain gradually set in. About 3 days later I realized a lot of shoulder and arm pain that also happened came from knots in the armpits. It took me several hours to get all but one worked out. They usually come back again several times.
I wouldn't be surprised if the chest pain you mentioned is also due to a knot. However if you can't find one nearby, I think the chances are high its a knot in a neck muscle (trigger point) that refers the pain elsewhere. With me several knots happen occasionally which cause shoulder pain. Sometimes simple turns of the head in certain directions will cause presure on the knot, triggering the pain elsewhere.
The most frequent spots I find knots in neck are the muscles that go below bone, such as collar bone. Usually I can find a muscle by touch just above collar bone, then raise chin upward(exposing more of the muscle) while feeling along the muscle. Basically from shoulder to shoulder I develop knots below collarbone that will refer pain elsewhere, either into shoulders or chest usually.
There are also trigger point injections, that you can get for the knot. I've never had them but have heard of a few fibromyalgia patients getting them regularly. But a really good massage therapist can help a lot, one that's not very skilled will help not at all, or even leave you feeling worse.
This book:
http://www.amazon.com/Trigger-Point-Therapy-Workbook-Self-Treatment/dp/1572243759
is highly recommended by almost anyone recommending self-massage books. I bought one myself 6 months ago, but still haven't read it.