Posible side effects of the B-12/Lipoplex Shot

I received my first b-12 shot on Saturday and noticed that my left hip was sore about 5-10 afterwards. I assumed it was because I tensed up when she gave me the shot. The shot was given on my upper left buttock. It is Monday morning my left hip is aching constantly. I woke up early this morning and couldnt get back to sleep because of the nagging ach.
I called the DR this morning and she said that this could happen in patients that are not "overweight." She also advised me not to take anymore shots- but to take ibuprofen and rub aspercream on the buttock.
I searched and searched the net looking for possible side effects and couldn't find any. The doctor didnt even mention this. Has anyone had any problems like this? I have lost 2lbs since Saturday and my appetite isnt really there because of the suppresants.