I had a sebaceous cyst removed and the incision opened after stitches removed. What should I do? (photo)

You should keep this wound clean and moist until it closes. After that protect it from the sun with sunblock and keeping the area covered with clothing. The scar can be revised at about 12 months after the initial surgery if it has not improved to your satisfaction. However, this procedure will carry some risk of the incision reopening. I am not sure who removed the initial cyst but you will want to ensure that whoever you consult with regarding a possible revision is a scar treatment expert.

In our office in Los Angeles, we use an early scar therapy protocol that utilizes both laser and topical therapy to improve your scars. Raffy Karamanoukian MD FACS

Once a wound has opened, it needs to be treated with local care and the area allowed to heal secondarily.  Closing the wound, whether using steristrips or sutures, would carry a higher risk of infection.   It is impossible to assess your scar healing at this point but, if you are unhappy with the result, you have the option of scar revision down the road.  Also note that the chest is an area which classically does not heal with fine line scars so expectations must be realistic.  Discuss with your surgeon and, if the procedure was not performed by a board certified plastic surgeon, you may wish to seek out a consultation as the healing progresses.