Just keep an eye on it for now. The main thing is you know where the blood came from so you can keep a watch for infections. I don't think it looks angry & like you said, she's fine with you touching it. She may have caught it on a splinter from her platform or has she chewed any plastic in her cage giving a rough edge she may have squeezed through? Anyway, hope she's okay.
P.S. If it helps, if you're using photo bucket there is an option to resize, if you click on the photo then some little icons appear including an editing one & resizing is in that. Ignore me if you know that already - it took me a while to twig that option was there
