Strange Swelling On My Bichir

[Azaezl]

I've posted this in the emergency section also, but thought seeing as it's about an oddball, posting in the oddball section might get a faster response.

My senegalus bichir has developed a strange swelling near it's anal fin, he didn't have it this morning, it came up about an hour or so ago, I'm totally stumped as to what it could be, part of it almost looks like a slightly brown / orange colour which makes me think it might be some sort of fungus

Either it is some sort of fungus or I have sexed them wrong, it's not the male and actually a female who might be swelling up with eggs(I don't know much about breeding habits), the 2 bichir's I have usually keep out of each other's way but yesterday evening they were together for ages in one of their caves almost laying on top of each other. They have also been swimming together and generally been near each other all day.

Apart from being slightly swollen he / she is fine, eating, swimming about happily,as are the rest of my fish. I haven't observed any nipping, which I doubt would happen as they are all peaceful with each other.

Here's a few pics of him / her, any help much appreciated;