Hi
I don't know anything about medical matters, but could it be an infection that occured when you fell off the trail bike, dirt and germs might have entered your leg?
definately a trip to a doc, not the nasty one though..tomorrow, you might need a course of antibiotics?
Your sister in law will know a 100% more than I do though! Either way, go tomorrow and get it treated somehow!
Chin up, try some painkillers to make yourself comfortable, and phone for an appt in the morning hun x
Don't think the worse, until it is diagnosed tomorrow. Can your sister in law come and have a look at it this evening, and give you a close up, off the record, opinion?..before you see your own doctor!
take care x