Female biting male

Question
We got a 6 week old male guinea pig over 3 months ago and adored him so
much that we decided to get a female. We fixed him first then got the female.
At first, there was a lot of noise and running around but we had read that this
would happen so we just let them get used to each other and they became
friends.

He would follow chase her around but recently she follows him around
sniffing his butt. But now, I actually see her looking as though she is biting
his private area from the back. And he doesn't seem to enjoy it much :-(.
There was time that I was feeding him carrots and  she went up behind him
to do that sniffing thing she does and he made a squeaking noise.

Although, i haven't exactly seen her teeth come out since her head is always
hard to see, I am just assuming she is nipping him. I have a feeling that it
hurts him. He now has a sore in his private area.

I had heard that it was just a dominant showing by the female but I am
worried.

Other than the sore and the running away from her when she gets into those
moods, he is eating and drinking fine and thoroughly active.

What should I do about her biting him down there? Should I take him to the
vet?

Answer
Hello,
it sounds like she is doing the dominance thing with him and actually biting on the rump is normal actually.
I would try to put some neosporin on it and if you feel that it's necessary, I would take him to a vet, but if it's just a sore and it's healing I wouldn't worry about that. Like him trying to dominate her, she's doing the same thing and it should settle down as it has done before.