If it's turned yellowish and hasn't dried fully yet, chances are there's inflammation /infection. That explains the hurt too. Because it was a bad scrape, it might take longer to heal and while healing, it may go through phases of scabbing over, but not fully yet, and turning ***** and inflamed. This is especially true if the scrape is on a body part that bends/flexes all the time eg knees, elbows etc.
I haven't yet been able to figure out fully if keeping the wound covered or open is the best-my guess is, the right combination of both. Have you thought of seeing a GP to clean it properly and dress it?