Since you want to apologize, it's very simple. You can go ahead and start a conversation, not loud, and say like,
I apologize for what I said. I already have an injured leg and when you stepped on my foot, it hurt a lot. So, I really didn't mean what I said at that time in pain. I hope you understand.
A simple apology won't hurt and it can set things right. When you apologize, keep it short and simple.
She might be unwilling to talk to you, but you don't know that. So, try it once. Also, make sure to not apologize in public or loudly. This might embarrass her and apologizing might not work.
I have been in pretty much the same situation as yours. Once I had my leg hurt and walked with a limp. I got on a bus and then stood in a corner to avoid the crowd. But a few minutes later, a girl stepped on my foot that increased the pain. So I yelled at her. I got off the bus but I realized that I shouldn't have insulted her as it was not really her mistake.
Next day, I saw her again on the same bus, I thought to apolozige but was hesitating. However, I thought I'd not get another chance again. So I just went and said the same words. She accepted the apology and also apologized by saying that she didn't realize that my leg is hurting until she saw me walking with a limp.
As per the comment by David K, she may or may not accept the apology. So, if she accepts apology, then it's all good, but if she doesn't, then don't bother her.
As per the comment by Kevin, you can also add this instead of "I hope you understand"
It was a terrible thing to say and I'm sorry that I said it.
