Took 3 doses of clindamycin now have nasty taste competing from empty tooth socket tooth pulled over 3weeks ago?

Most likely: drainage from infection or abscess. Rinse as directed and keep taking antibiotics as prescribed and the taste should resolve in a few days.

Probably infection is draining from the tooth socket: Most likely infection is draining from the socket if no rash and no fever not likely side effect of antibiotic rinsing with salt water will help to clear the area