How long will it take for the stitched wound to heal?

I had a large birthmark (4.5cm by 1.5cm) removed from my back. It was cut out and then stitched up (no grafting) exactly 3 weeks ago. The wound must be about 8–9cm in length. Could you tell how long more it will take to heal and to cover up with skin? It still hurts when I bend etc.