Ya bud this is common not to worry it will go away.
Like acne said you just nicked a blood vessel it happens, but when you finish taking out the needle do not rub or massage the area just hold the tissue there and just apply pressure.
Some massage the area which will cause a bruise.
People who massage the area after injection do it mostly cause they don’t want to have the muscle stiffen up, but the correct way would to wait 15-20mins after injection to make sure any blood vessels have closed that might have been nicked and then from there just do some stretches on that particular muscle.
Hope this helps,
Slider