is it warm to the touch? is it red? where is it? your body tends to get used to injections after a while... next time warm up the stuff and massage the area afterwards. 3ml is a relatively large amount of liquid for your body to disperse.
if it's warm or red then keep a close eye on it cause you might have an infection or an abscess so be ready to go visit the doctors office. that's probably not what it is tho, just be wary.