What Causes Left-sided Chest Swelling And Sharp Pain In The Arm Pit?

2 weeks ago I had sharp pain in my armpit area..4 days later, the left side of my chest swelled up greatly and I went to the E.R. they think I tore a pectorial muscle..it started to bruise severly on my left side..2 weeks have gone by and the bruising has gone down, its almost gone, but now all of the sudden, I have a 6 inch bruise on my left side and a 4 inch bruise on my right side, both perfectly right above my hip bones. theyare sore and tender to the touch..what could this be?