2 weeks post extraction, foul taste is due to the saliva from healing area. so, be patient and let your surgical area heal properly. Dont poke that area with tongue, it will cause further infection. Once the healing process is complete, the bad taste will automatically go.

And if you are more concerned than i would suggest you to visit  a dentist and get the area manually checked. Make sure to go to a dentist whom you visited previously....At home you start doing warm saline gargles and don't eat hard stuff from that area. For more info find the link below....http://www.identalhub.com/article_do's-and-don'ts-after-tooth-extraction-153.aspx