Please, any feedback is appreciated

Hi, This is my first post, as I joined this group souly due to this reason. I have a 8 year old, blue heeler mix. Very healthy, happy [even wags in her sleep], with no significant medical history. While camping this weekend, a friend pointed out that she has a hard, UN-movable, lump under the skin. This is located under her left eye (NOT eyelid), between the eye and the base of her muzzle. The skin can be freely moved over the lump, which is solid as bone and feels attached. When pressed, it does not secrete any liquid, and does not appear to cause her any distress or pain. There is no scabbing, loss of hair, or redness on the skin itself. I keep telling myself that while we were camping she took it upon herself to chase all bees away from the camp site, but we never heard her yelp, there was no noticeable allergic reaction, additional swelling, or visible rash. The lump has been observed for three days now, and other than a small size reduction over the first night [possible wishful thinking], has not changed. I know the first thing to do is the vet. I am terrified: last December I lost my 8 year old cat [which i rescued and bottle fed] to pancreatic cancer that was silent until he went into renal failure. Pepper is now the same age as the cat. I am a medical student, and $$ is very tight, although her life means more to me than money could every buy. My medical mind is telling me cancer, and I feel like I need answers, although the vet is on Friday. Hard, UN-movable, under the skin, no discharge, no pain when pressed. Even if you tell me i am right.... someone PLEASE tell me something... personal experience... or if there is a vet out there advice... I just don't think I can stand to loose her too... I am 10 hours away from my family... when I left home for school I had her and the cat. I was always ok because I had her and the cat.. and right now I am crying and can hardly breathe... any information.. anything Please: about the lump, or about any financial assistance I may be able to reach out for during this (charities, organizations, can we go to a vet school for a reduced fee?). Thank you..

Sorry to read this. Firstly we wouldn't know about possible assistance as it seems you are not in the UK.
I think the best thing you can do is go and have it checked out. Unless of course in the next day or two until you can get to the vet it reduces dramatically in size. In which case it is more than likely as you thought a reaction to something.
Not all lumps mean cancer but if you are not sure and it doesn't seem to reduce in size or it gets bigger or changes in any way it is best to have it checked to put your mind at rest apart from anything else.

The way I see it is it's better to know for definite than worry yourself sick needlessly. See a vet it's the only way to actually know for sure what's going on. By all means wait a week and see what happens but if it grows or she seems uncomfortable see a vet. Borrow the money if you have to or use a credit card. I lost a dog at 8 a couple of months ago to bone cancer and if it's any consolation it normally starts in a limb not the face, not sure any other cancerous lump would feel like bone to be honest. Just see a vet and stop tormenting yourself with what if's.