I dont post here much but I had to say I am really sorry to hear about this, but fingers crossed it will be nothing serious.
Excuse me giving unsolicited advice, but I have worked in the NHS for 10 years and picked up a lot of health advice which may help you right now.
I guess thats the first piece of advice to give you, "Dont waste time worrying about something until you KNOW you have something worth worrying about" (thanks Mum for that one

).
If you are worried dont be afraid to go back to your GP or any GP in the same practice if your GP is away and ask for answers, thats what they are there for and will understand completely. Dont be afraid to give them a hard time and stay beyond the 10 min appointment if you need to (but the nice approach normally produces more results).
You seem to be taking it well and thats the second piece of advice, "Talk to people about it, preferably in real life". You can scare yourself half to death by reading stuff on the Internet and then deciding it sounds just like you. Listen to the medical professionals and ask them anything you want, there are no silly questions when it comes to your health and mental well being.
IF you do get a confirmed diagnosis, there are lots of really good support groups for health issues (MacMillan, etc) and your GP or NHS Direct can put you in touch with them. I know some people hate this sort of things, but having had a girlfriend with cancer I know they work very well and well worth attending. Again, once you get a confirmed diagnosis, get your benefits sorted early as you already know how slow those wheels turn!
Third I would say is that the people I have seen who get through this sort of thing (whatever the diagnosis) most are the real fighters who keep a positive mental attitude. You are young which is a fantastic thing to have as any treatment will take a bit of stamina. Just make sure you eat well, sleep as much as possible and dont go wearing yourself out.
I wouldnt worry about the X-Ray. Certain types of cancers have a predictable pattern about where they spread to. Having "no further action" is a VERY good thing as it means that IF it is a cancer that it has not spread to your chest.
You will know this by now, but Lymphoma is a cancer of the Lymph Nodes (or known as Glands, when "your glands are up"). Normally swelling and tenderness of these nodes are from infection which has spread from somewhere else nearby (think having a cold/flu and your "glands" in your neck swell). The Lymph system is also spread around your body and these nodes/glands can be commonly felt in the groin, armpits and neck, but you do have many others internally which you cannot normally feel and may also be what they were checking on the x-ray.
Lastly, I hope this has been helpful and not overly preachy.
Good luck, fingers crossed its is nothing serious and remember to eat well, sleep well, FIGHT and you WILL get through this (whatever it is).
