Grace's experience with the embedded grit made me think, how about an warm epsom salt soak or cloth? I've had good luck with bringing deep infection and embedded debris to the surface with epsom salts. Apply for 10 minutes, dry it, finish with a light coating of antibiotic ointment (3 times a day). If nothing else, it will be really clean!
A doctor taught me how to do this, years ago, when I had an abcess. It's a good, gentle therapy.
Gail