There are several brands of the foam dressings around. Some are just to stop bleeding, but others actually are forming a bridge to help cells migrate across the wound and speed healing. Not knowing what exact one was used, I would call the ER and ask how much longer. Alternatively, call your primary care provider and ask if they have gotten a report from the ER and ask them how long it should take. Since they told you to not remove it, I suspect that it is forming a "cell bridge" and removing it would just re-open the wound. My experience with these sponges is all veterinary, but they give amazing results in non-sutureable wounds in dogs & cats.