my 2 rats got into a fight

Question
I had 2 girl rats from the same litter and recently got 2 boys to breed them with. 1 of my boys tried to play with one of the girls and she freaked out and attacked him. Only he bit her toe and made her bleed an awful lot. She didn't seem to care that she was bleeding and has been walking on her foot and playing with people and her sister. But after this happened she's been very tired,like hiding under blankets. and when i tried to give her a carrot she didn't want it. should i be worried? her personality has changed around people or her sister but she's never turned down a carrot and never not finished one.

Answer
 First of all, I would not recommend breeding your rats.  There are so many unwanted rats in the world, and so many people breeding rats with unknown backgrounds and perpetuating bad genetics starting from pet store or laboratory lines.  If you're wanting to be serious about breeding, do a lot more research and start with well-bred rats from a reputable breeder that are excellent examples of fancy rats.

 That being said, I will caution you not to just throw the males in with the females, especially in their cage.  The female likely attacked him because she was feeling territorial or scared.  If you think of it from her perspective, a huge man just walked into her house and tried to mate with her.  I would be freaking out too!  She is probably just very scared and will eventually calm down if you remove the males from their cage.  If she's still walking on her foot and it is no longer bleeding then it's probably not a bad injury but if it gets swollen, hot, continues to bleed, or is leaking pus, you'll have to take her to the vet to have it properly cared for.

 If you do plan to breed your rats anyway, please make sure you do as much research as possible so you can make the experience as stress-free as possible.  You also probably don't want to breed the both of them at once, or you will quickly end up with over 20 babies which can be very hard to rehome if you don't want them to end up as snake food.  Also, make sure you remove the males from the cage before the females give birth or they will breed again and have a second back-to-back litter which is very hard on both them and the babies.  For more information about breeding please check out my website at http://careguide.evergreenrattery.com