What Causes Red Itchy Rash Below The Knee?

Hello, I have a question regarding a rash on the back of my knee below the knee crease on the lower leg. It s quite red, itch, round rash It has a red demarcation slightly raised border and red in the middle. it started out small but got bigger. At one point it was oozing-began to look like a burn, after using a candescent lamp near the rash to heat, that has stopped. In addition, using a oregano oil base with olive oil and other nutrients it dried and crusted over. However, It has some areas that has peeled, but it s still red underneath and itchy. It s now been 3 weeks. any suggestions? I don t remember being bit by any bug or anything. I thank you in advance for your help.