Hello~I have put in a reqjuest for your post to be moved to men's health. Hopefully someone there will be able to come up with some suggestions and ideas.
It could be something akin to Athletes foot, a fungus. Not really an open sore, but red areas, treated with Clotrimazole twice a day it went away after awhile. Because there was initially a bump the Dr. thought it might be genital warts, I was told to ask my girlfriend if she had ever had an irregular Pap Smear, a common sign of gw for women.