Woke up with a bruise on the middle of my left bicep today. felt some discomfort before my workout on wednesday, but went ahead with the workout. trained back and biceps. hit it hard with biceps. is this from the workout or something else?

Bruised muscle is likely but vigorous work out without a direct strike to the muscle should not cause an isolated bruised muscle. You just ice the area, take ibuprofen OTC as needed for the pain, and you can work that muscle again when pain subsides with a lighter load then gradually build it up. Try to recall if you had a contusion which could be mild to that biceps before Wednesday.