Bird Hurt Foot

Hi, 

I left my budgies (2, both female) at home for two days alone (plenty of food and water). When I came back, one of the females had a hurt foot (there is no way the other bird could have attacked please so not tell me otherwise), and was quite lethargic and weak. She seems very awkward when walking around (trying to spread wings out for balance but tipping over) and falls to the ground a lot (left leg).  When she does fall sometimes she just sits on the ground and doesn't get back up. Any home remedies? please answer ASAP thank you :))