Ask a Neurologist. Get Answers to Your Neurology Questions.
How large would you estimate this lump is? How long has it been there? Is it red?
has it been enlarging?
does it compress easily like a fluid-filled sac?
Yes, this could help with the pain. A pain cream such as aspercreme or capsaicin might also help a lot...both are available over-the-counter.
Sorry that answer was intended for another patient.
A stable, fluid-filled sac might indicate arthritis in the knee joint with an "effusion" or fluid in the joint pushing out against the joint capsule.
Another consideration would be a cyst (e.g. Baker's cyst) which is an out-pouching of the joint lining that fills with fluid. If indicated, your doctor or an orthopedist can aspirate the fluid and send it to the laboratory for investigation of the cause.
If you think this lump is not adjacent to, or connected to, the joint itself, it might be a sebaceous cyst, which can arise anywhere and fill with a compressible liquid cheese-like material. This can also be aspirated or drained by a dermatologist.
You could start with your primary care doctor or an express care physician. He or she will be able to direct you to the proper treatment after examining the lump.
The first thing to try would be an anti-inflammatory such as ibuprofen or naproxyn sodium, if you tolerate them. Next would be a pain cream such as aspercreme or capsaicin. These agents can be very effective for controlling localized pain without causing systemic side effects.
If these medications are not effective, you would need to ask your doctor to consider a nerve-stabilizing medication such as gabapentin or pregabalin. These are well-tolerated, effective medications for nerve-related pain especially.