Asking medical advice on the internet = NEVER a good idea. According to most horror stories, no matter how small your injury you will die from it.
Chill for the time being, check if it gets bigger and go to the next appointment. It might not be anything to worry about, but it's safer to check.
I panicked over a lump recently at the back of my neck, only to find out it was a gland and nothing to worry about. However, it could have been worse. You can't be sure until you seek medical help so there is nothing you can really do about it now.