Why is my chest so sore? Please help!?

I think it was Thursday When I noticed that I had a little pain in my chest above my right breast it spread over to my shoulder. I have been doing Zumba for about 2 weeks now, it started the first week I started Zumba again. The pain isn't that bad I can stand it. Could it be a muscle strain? If I did strain a muscle how long will it last and what can I do to help it heal and still be able to workout?