Mouse Has Big Cut On Ear and Chest

Hey guys, so I have 2 pet female painted mice, and one of them is worrying me. I recently discovered a pretty large cut by her ear and exposed flesh/cuts on her chest. Observation leads me to believe these wounds are self inflicted, for I never saw the other mouse 'bully' her, and I have never heard noises coming from them that would mean any foul play. I will try to get pics up later. I am worried these will become infected and that she is in to much pain! Please help! thanks in advance
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It seems that she is obsessed with cleaning herself and is constantly scratching herself and making it worse as well, it seems like she cant walk on one leg well either.

That sounds like fight damage. Are you sure they're female?

she's trying to clean the wound. mice do not have enough emotional intelligence to even contemplate self-mutilation.
and it's hard to imagine a mouse biting its own ear or it's chest, is it physically possible?....
99% it's from a fight. you don't see it because the mice are probably more focused on you when you're around.......signs of bullying would be bites on the tail or rear feet, bites at the front end are from real fights.

Sometimes they over-groom (or they over-groom each other) or sometimes they scratch at themselves. Mice I used to work with used to develop ulcerative dermatitis where they scratch at themselves until they develop lesions and sometimes they get infected. Sometimes it starts out with the whole over-grooming business and it usually appeared around their noses and especially ears. Sometimes necks too. We used to trim their back paw nails (be very, extremely careful--not recommended) and slap on an antibiotic ointment. Do you have any kinds of "enrichment" items in the cage?

It also might be best to separate her out from the cage just in case.

I did separate them so if it is fighting she should start to show signs of recovery, and what do you mean by items of enrichment?

Hi, when I worked with mice, we used to put things for them to shred. We had little pulpy squares for them to tear apart. Not sure where they got them, but I'm sure you could find a pet store that would have little things to keep them occupied. What kind of bedding are you using?