The left side of my chest under my breast is sore also i feel like its twitching ?

Muscle spasm: Somehow you strained your pectoralis muscle. Give it some time. Try massaging its tender attachment found under your arm pit.

Is it tender: I suspect this is what we call a Tietze's syndrome also known as costochondritis, Which is inflammation of the chest wall cartilage but I also feel it is the muscles. You can try heat or cold on it, if it persists you can see your physician to clarify the diagnosis