I have a sudden red, inflamed and very painful lump on my penis shaft. It is about 1 cm in diameter and only appeared a few days ago. I am not sexually active and there are no there symptoms. What could it be?

If you are not sexually active it may be an ingrown hair, cyst, inflamed pimple, infected cut, etc. but you should go to the doctor and get an anti-inflammatory or antibiotic to get rid of it, or have it removed, depending on what it actually is, they may have to do a biopsy on it, but they will numb the area first so you will not feel it.