Every drug has side effects, but once you start antibiotics you really should finish them. The side effects of antibiotics are exremely mild and rare I seem to recall, but it has been a while since I did any research on them.
Hairline fracture should take a few weeks to heal, but that will vary wildly based on age and general health so it is hard to say. The delayed concussion symptoms should clear up in a day or two based on my past experience.
Just resting is almost certainly the best idea for this list of problems. They will all clear up on their own.







