A week-old knee wound of this size with a yellow centre and limping needs a professional medical evaluation to rule out a deeper infection. For daily care, switch from povidone-iodine to washing with sterile normal saline, as iodine can actually delay tissue healing. You can apply a generic topical antibiotic like mupirocin or bacitracin ointment to prevent infection and keep the wound bed moist. Cover it with a non-adherent sterile dressing. For pain and swelling, you can take over-the-counter acetaminophen or ibuprofen. Please consult a doctor promptly to safely manage the wound and ensure proper healing.