Mystery lump in udder, any ideas?

[LD&S]

My cob is 7yrs and has always been ultra sensitive any where near her udder, gradually I've been trying to get her used to me touching her more sensitive bits. She's never been in foal.
On Friday I was actually able to touch her udder very briefly and it felt like her teat was a hard lump a little bigger than a grape and quite round, the skin felt taut though smooth, it was only a very light touch but she was far from impressed. I rang the vet and he is out later today.
Over the weekend by gradually running my hand up her leg she has let me touch it, no squeezing but just to get her used to a hand there ready for today. I was really surprised, when I knelt down from the other side it wasn't her teat but a lump on the udder.
Has anyone any idea what it might be?

 

[Sukistokes2]

Could be anything, I'm not one to run to the vet at the drop of a hat but lumps are one thing I wouldn't hesitate to call over. My mare used to love her teats touched she would come over peculiar if you washed them. You mares reaction make me think they might be sore. However all horses are individuals of course.

 

[LD&S]

I don't think her lady bits have been touched much as she can be funny about the top of her tail too though in all she is getting much more relaxed about me 'fiddling'.
At least I won't have to wait too long as vet should be there between 1.30 & 2.30 and I've never known him late.