It depnds on how long after the injections you're having these reactions.
If it's right away, it may be a normal response to the trauma of this (or any other) injection. Injections involve the insertion of multipel needles (or one needle multiple times) and that process can cause some redness and warmth, similar to having sustained a non-medical injury to that region. If, however, it's several hours or days later, or is persisting, then you may be having a reaction to the material or, in its extreme, an infection (cellulitis).
Iin either event, you should talk to your physician asap about this...a possible cellulitis is not something you want miss or to delay in seeking treatment.
I hope that this helps, and good luck,
Web reference: http://www.bodysculpture.com