Please don't take this as advice if it's your affected foot. Go see a doctor.

I've had problems even predating the RSD with this. The trick is to find it early while it's still just irritating the skin. Under these conditions just apply an over the counter product call OutGrow on it. This stuff turns the skin to leather and allows the nail to grow up over it. Once it's infected you'll have to cut the nail back and start over probably. Keep it cut back until the infection is completely gone and then use the out grow.

Trimming the nails properly is important to stop these from recurring but RSD tends to destroy the nails so you may find the problem less avoidable. Cut the nail as straight across as practicable leaving the edges free of the skin. There is a little "runner" that grows uder the nails at the edges. Don't pull on this if you see it. Just cut it off.