I dont have a whole lot of boarding experience. I am a true newbie. Have been taking lessons every weekend for the past month or so.
But I was a nurse before I changed career direction and went into the legal field...and then became a stay at home mom. I will say that the break in that bone is pretty high (as others have stated). Do much more damage to that area and you will spend the rest of your life wishing you had listened to the doctor.
Personally I would not risk it. PLUS, I have to give my opinion as a mother as well. If my 17 year old had this kind of an injury I can tell you right now that they would not be boarding again this season. (my daughter is 7). Maybe that makes me sound like the mean and cranky old lady of the group...and I am ok with that. (I am only 32) What do your parents say?
On a final note...this entire thread has kind of freaked me out. lol My first lesson my instructor told me that if I felt like I was losing control or was going to fall I was to ball my hands into fists and tuck my arms in. She said broken fingers happen all the time.