For home remedy just givie it plenty of rest, applying an ice pack wrapped in a tea towel for a bit of swelling, and keeping it gently elevated on the sofa. But it's already been weeks and the pain doesn't settle down soon or they're still struggling to walk on it normally, I really recommend getting it properly checked out by a professional, we actually take our little ones to see Dr Alan Cheung, a Knee Specialist who made us feel reassured.
Honestly I'd bring him to see the PD sooner rather than later, especially since it's been weeks and still hurting lah. A simple fall can sometimes be more than it looks, and the doctor can do a proper check to rule out anything that needs attention, then give you actual treatment instead of guessing at home remedies. Once you know what it is, then you'll have peace of mind and can help him recover properly.
Honestly, if it has been hurting for weeks and home remedies aren't shifting it, it might be time to skip the home fixes and look into getting a proper surgical opinion. Dr Alan, my doctor always says that persistent joint pain in kids often points to a mechanical issue that won't just heal on its own with rest. It is definitely worth booking a specialist consultation to see if a small procedure.
Serene Lau