Beleive me, most of the companies don't tolerate sick days! Just ask Etihad or Ryanair or any other crew.
I think it's legal what they did. The same thing happened to me, too.
If you want more (and reliable) information, read though the flight time limitations in the SEP Manual OR do the on-line course in the learning zone (availabel for all crew: you can do it at home or in the library at the college).
Call sick if you are sick. What can you do?! If one day is not enough, call sick longer. Even better: go for the flight and try to get a note about industrial injury, so your sick days won't affect your career (upgrade).
I hope your injury is not serious.