swelling after ankle surgery

hello, im anthony...i jus had a lengthening of the aquilies tendon, it was released about 2 inches...the tightening was due to an accident that occured about 7 years ago. i am 19 now...i jus had my surgery and recently finnished my time of 2 months recovery. i jus started therapy today. im worried cause when i try and walk it hurts and i have pains ive never experienced before the surgery, its not infected. there is swelling...as therapy goes on, is swelling ok to have should i be worried. will pain decrease by stretching it and workin it even though it hurts. as they say "no pain no gain"...can that be used in my case or should i use precaution. this is a 1 shot deal and i wanna do it right. any professional advice would be nice. Thanks.