That's actually pretty common, happened to me 15 years ago. Happened to my SIL just this past weekend. Definitely go see your OB, s/he is the one who performed the surgery.
Did you have internal and external stitches? I had a c/s a little over three years ago with my son, and went to the ER because my incision had started to open in a small spot, but it was just because I had internal stitches ONLY and the outside had been taped/glued whatever, there were no stitches. It was absolutely DISGUSTING!!! There was some puss, and it was red and very sore, BUT it was only the internal stitches making their way to the incision and coming out. I had started growing pubic hair back along the incision line and it was hard to tell the stitches from hair, but I pulled out several stitches that had come to the surface, they almost to begin with looked like an ingrown hair...I had it happen up to 2-3 months after the surgery. BUT your OB is definitely the one to see...
Whatever dr did the c section
Your OB. In the US, most OBs will continue to be responsible for your care until 6 weeks post-partum, and with a c-section he is absolutely the person you need to see.
I wouldn't put this off...call as soon as they open! Wounds DO have a smell to them when they heal, but a c-section incision is nothing to fool around with as it involves your reproductive organs.
best of luck..update when you know what's going on!