Hello, I Had Unprotected Sex And I Have A Round

Hello, I had unprotected sex and I have a round red rash on the head of my penis...It started out small but has spread larger over a week..my partner doesn't have any rashes on her vagina but she did have a cold sore on her nose that just recent went away. Her vagina does have a kind of bad smell around her clitoris when the skin is pulled back. What could the issue possibly be and should we be worried?