Recently I have been clenching my teeth at night, and the other day I had crunched down on something hard (may be a loose filling) and after that my back tooth and gum has been causing throbbing pain and every time I rub my tongue against the gum underneath the tooth it causes a lot of pain.
Hello, Welcome Thanks for consulting Chat Doctor, I have gone through your query, as you have habit of clenching this causes trauma to periodontal ligaments.  I will suggest you that you consult dentist and go for oral examination if pain is due to dislodge filling then go for restoration if it is due to periodontal problem then go for Scaling and Curettage.  Do warm saline gargle two - three times a day. Hope this will help you.