Well, if you are out walking, it sounds like your recovery is going great. Congratulations on getting active right away.
This incision appearance sounds like the normal healing process to me.
When they removed the bandage and stitches, did they give you a list of things to watch for?
Usually these are:
Wound opening/bleeding
Redness & new tenderness - especially with fever (possible sign of infection)
Weeping or oozing, other than small amounts of clear or blood-tinged fluid

Otherwise, remember that your body has been assaulted, and some swelling and tissue irregularity is to be expected.
If you are really concerned by any worsening symptoms, you can always call the surgeon's staff.
Sue