My toggle bolt hole hit a stud. What do I do now?
That sounds like a good problem to have. Go to the store and get a lag screw, and use that instead. 


(source: china-ogpe.com)  

Attaching the sink to a stud is preferable, and will offer a more solid install.

Hanging a sink from drywall, sounds like a bad idea to begin with. So I'd say you got lucky to hit the stud.