I have had a small pea sized bump under the skin of my right bicep for 3-4 months now. It s located on the inside of my arm, about 2.5 inches up from the elbow. The skin at the location of the mass is ever so slightly darker, but you have to look very hard to notice it. It doesn t bulge out from the skin, but I can feel it if I press on it, and it s slightly mobile. It has never caused me any pain, but if I palpate it, it will be sore, and sometimes causes a very, very mild tingly sensation on my right arm for the next day or so.