Baby has angry red spot on leg?

Hi, my 13 month old daughter seems to have developed a very angry looking red spot on her leg this evening. Of course it's Friday night and so I have all weekend before I can take her to the doctor if need be but I was wondering if anyone knew what it might be. Its probably silver dollar sized and really really red, almost purple in spots but it doesn't really feel raised or rough. If I touch it she doesn't seem bothered but it looks really scary almost like it could break open and bleed anytime. I cant think of how she might have gotten hurt or anything, it's on the inside of her thigh, about midway up. I don't think her pants should have rubbed a raw spot or anything. I put some triple antibiotic on it earlier and wrapped in in gauze but she couldn't sleep because of it so I took it off. It didn't help any but it was only on for a few hours. I'm at a loss. I know its sort of a vague description but I don't know how else to describe it. Does anyone know what it might be?