I am a professional athlete and have a case of tonsillitis with a black tonsil and a little fever. i would like to know how long before i can exercise?

Checked for strep?: A person with tonsillitis can be checked for strep throat at her doctor's office. If there is strep, antibiotics are needed (usually amoxicillin). After 3 days or so, she should be well enough to gradually begin exercising again. If her symptoms are viral and start improving after 3 days, she should be able to gradually resume exercising then too.

Common sense: Wait three days minimum after fever breaks, rest, hydrate. Pace self.

You need to be exam: Tonsils are usually not black. You should be seen by an otolaryngologist.