@Annabelle if you have gone to reputable clinic then I see no harm. Physios are well trained and I could not imagine one who doesnt want the best outcome for their patients. If at all worried I would recommend ringing your breast care nurse.
I would even have a chat on the phone to the physio telling her the scar seems bigger.
In my experience most professionals want to help. You did what you thought best . I also believe the physio would not have treated you if they thought it was going to be harmful.
