A pimple under the tongue is simply called a tongue pimple, explains WebMD. Tongue pimples appear when bacteria gets under the surface of the skin on the tongue.
The most common causes of a tongue pimple include allergic reaction, clogged pores, viruses, consumption of hard foods and tongue diseases, like thrush or oral candidiasis, explains the free dictionary. Those with tongue pimples should resist the urge to pop them. Popping pimples can spread bacteria to other places of the mouth, warns the Huffington Post. Treat tongue pimples by chewing mint leaves and gargle with mouth wash two-to-three times per day.