I know someone that had the same thing in their shoulder. They sucked out about 5 cc of pus and it went away on its own. Not a good idea to do that, once you poke it then it has a greater chance of spreading. Sterile is used to describe it because it is contained, it hasn't spread, and you have no other symptoms such as fever, redness, pain, etc. To be safe go to the doctor, they will lance it and probably prescribe an antibiotic as a precaution. Do not squeeze it yourself. If you don't get it all out, then it has a greater chance of spreading under the skin since you squeezed it. See these things all the time where I work. Most aren't gear related though.