I would suggest that you schedule an appointment with the surgeon
who performed your cyst excision. A small hardened collection of material in an area where you recently had trauma could be a number of things. I would say that this is unlikely to be scar tissue since you had this cyst removed just four days ago. It takes much longer for scar tissue to develop. I would say that hematoma (which is a collection of blood) is one possibility. If it is a hematoma you should expect it to resorb naturally over the next week or so. It also could be just a collected area of fluid such as general swelling in the area. This too should go down without any problems. The only reason that this area would not resorb is if the cyst was not properly removed. If the cyst walls are still intact, then fluid can collect again in the area and remain. Again, I would suggest that you schedule an appointment with the surgeon who performed your cyst excision. He or she can examine your one and determine what is causing the swelling. If it is not clear from the physical exam, he or she might perform an ultrasound
to look at the texture of the swelling. If it needs to be re-drained that can usually be done in the office. Most likely your surgeon will recommend conservative therapy and observation to see if it gets better on its own.