With a bruise that small, it's just a small vessel near the surface that you punctured. Nothing to worry about...it'll heal up in no time. Since you said thigh, I assume a quad shot. Be thankful you only ended up with a bruise! The 1st (and only!!!) time I shot my quads I put 2ml of Laurabolin in each. Had the worst knots in my muscles as a result: could hardly walk. After a session with a massage therapist that almost made me pass out from the pain, I walked out feeling better....and with a knowledge that it'd be glutes only from there on out!