Lower right wisdom tooth and dentigerous cyst removed.now there's a deep hole in my gums and foul taste coming out of it.it's infection?can i stop it?

POSSIBLE INFECTION: See the dentist again sound like you need an antibiotic, asap.

Infection/dry socket: Foul taste usually indicates infection; not unusual to have a dry socket following a difficult surgical extraction of a lower molar. Return to the dentist to place medication in the extraction site and they will most likely also prescribe an antibiotic.

See an OS,: Oral surgeons, also called maxillofacial surgeons, are trained to detect, diagnose, and prevent defects and diseases that affect the mouth, jaw, teeth, and gums. Your condition requires a specialist treatment. Good luck.

Dry Socket ?: See the oral surgeon who removed it for post operative care. you're right, it may also be infected.

Probably: See the Dentist or Oral Surgeon that treated you. Additional management probably required. This is most definitely is not a DIY situation.