Sounds like you have torn the bicep. The purple/dull colour will be bruising where the blood has rushed to the tear.

Rest is the only cure i think. Doc may give you some pain killers if need be.

(Just my opinion, i aint no doctor but from how you describe it sounds like the most obvious diagnosis)

P.S. The dull ache your arms had after the gym session would just have been DOMS (Delayed onset muscle soreness) from your workout, totally natural, i doubt it will be related to your injury.