E.P.
Hi T.!
Couple things....You know your son. It doesn't sound like he's making up the pain so.... yes, either ride the Dr's butt or,better yet, find a new dr.
You say he was given an antibiotic - that seems to indicate that the Dr. felt he had some type of infection. A cheap way to get some free advise is to visit a local, trusted Pharmacist and see if this is something that makes sense to them, as far as the medication that was administered for this condition or any other advise that they can give you to treat the pain/reduce the swelling. You should have a local Walgreen's that is open later, near your home. Doesn't sound like he's had any fevers, which is good, and tiredness can be a sign of infection or he can be exhausted from being in pain or from being on pain-killers.
Has he had any recent bloodwork done? Are they associating the headaches with this "growth" ? The concern with a benign tumor is that it still can grow and press against vital areas of the body and cause pain and compression of which your son may be experiencing. I would ask questions about the "compression" part....what exactly is being compressed? size of the mass or cyst? Will it need to be drained or removed since it is not going away?
Again...you know your son. It sounds like he is really in pain over this and it's concerning that there hasn't been a reduction in size or pain intensity. As far as treating it... the hot compresses and hot showers can't hurt. Personally, if I didn't see ANY change by tomorrow, I would be back on the phone, asking these questions to my dr. possibly getting bloodwork done... travelling/iincreasing pain is concerning.
Best of luck to you and your son.