Well, I would say elides, rather than glosses over. There's a jump forward in the timeline following the accident and the bloody collapse at the drum kit, and we can assume that the accident and the other fallout from that day are dealt with (in fact, we see flashbacks to the expulsion letter). I think that was a good choice, actually: the accident and its immediate repercussions* could be a whole other movie.
Also, is it technically a hit-and-run if the person who was hit does the running?
* I'm not proud of my word choice here, just so you know.