I suggest sending the picture(s) to your vet.
I am not a vet, but it looks as though he has been licking or pulling at the stitches and there appears to be a little seepage.
We do have a member here with Veterinary experience... @agility collie mom can you lend a hand here?
Email a picture to your vet. Looks normal to me. There is no swelling or redness. Looks like a scab in the middle. Keep him contained for 2 weeks so the incision can heal without complications. Also either an cone or a pair of kids boxer shorts on backwards (pull tail though fly opening) to prevent licking. If he is really active you can ask for a sedative to keep him calm while healing.