I get a bitter taste at the back of my mouth when i eat something sweet. i was sanding some wood few days ago without a mask could that be the cause?

Yes: Inhaling particulates can impact taste and smell for several days after inhalation. Just provide yourself impeccable oral care for the next few days and consider investing in a tongue scraper, but this should clear quickly. The other possibility is a sinus congestion impacting smell and taste, so consider treatment with decongestants too. Finally, B vitamin deficiency can cause taste abn.