I had the same thing happen to me! You could have an infection in the wound. I went to the ER when my incision opened up, and they sent me home telling me to cover it and put neosporin on it. The doctor told me it was normal, because I had internal stitches and the glue stuff on the outside, the stitches on the inside were coming out, so my incision opened several times, and I could see what looked like a hair, but was really a stitch poking out, I'd grab the end and they'd come right out, it sounds disgusting, and it was. You could try going to the doctor, but I'd try neosporin and a bandaid, and if the pain got worse or you start to see puss, then go.
This is not normal. You need to call your doctor.
I know I had staples on the outside, but I'm not sure about the inside. It was really sore and tender for a long time. There was a kind of lump in that area for a long time too. $ years later The incision area is still a place that If i get bumped into it hurts more than usual. My scar did hear really well and is VERY unnoticable. I think that just takes a long time to heal however....
be VERY careful, because it can get infected easily. They sometimes have to re-open it and have it drained. better have it checked out.