I noticed a dark red lump under my tongue. it doesn't hurt, there is a slight discomfort if i put pressure on it. should i be concerned? what would cause this to form?

Likely blood blister: You may unknowingly hurt the tongue and there may have been bleeding into the tissue. Watch and wait for it to disappear. If it does not go away in a week, becomes bigger, or becomes painful, it would be prudent to see a doctor. For good health - Have a diet rich in fresh vegetables, fruits, whole grains, low fat milk and milk products, nuts, beans, legumes, lentils and small amounts of lean meats. Avoid saturated fats. Exercise at least 150 minutes/week and increase the intensity of exercise gradually. Do not use tobacco, alcohol, weed or street drugs in any form. Practice safe sex.

Many possibilities: Trauma being the most probable. Call your Dentist and let him/her examine the "lump." Any pain, bleeding, and/or swelling should be immediately evaluated. You have both pain and swelling. Please call now for an appointment.