Healing Process After Juvederm Voluma in Upper Cheeks?

Hi, I have recently - 3 days ago, had Juvederm Voluma in my upper cheeks to correct quite pronounced flatness. After 3 days they are very tender, & though no bruise is visable, seem quite pronounced and very hard. Moreso on one side. My Derm has advised they will soften, not to massage, but just leave well enough alone (and take arnica). I am very surprised at the hardness.. & a little worried! Is it possible that the size will indeed subside? Can bruising & swelling cause hardness? Thank you!