It depends on how far out you are from surgery? If its recent [within a few weeks to a couple of months], then it is probably normal post op swelling and healing.
But if its happening more than 3-4 months out from surgery, then its probably something that may need to be looked at a bit closer.
As always, please discuss your post op symptoms with your surgeon as he/she is the only one that truly knows what was done during the surgery.
Web reference: http://seattleface.com/html/dr_amadi.php