My lug nut snapped off. Is my axle "torn"?

I have a 2004 Hyundai Elantra with 100k+ miles. I got my brakes done twice at this same gas station...but anyway, my front tire was bald so one day I woke up to a flat. I tried driving it up to the gas station to put air in it, but failed. Thank Goodness there was a mechanic driving by. He came over & put my donut om my car, except the guys at the gas station put my lug nut on too tight, so it snapped off. Its been a good 3 months since then, and I hear creaking noises near the tire that my lug nut snapped off of. It also pops sometimes, you can feel it under your feet. I went to a mechanic and he said i have a tear in BOTH axles and i need to buy 2 axles. Do you think it could just be the "boot" or could it be the axle? Both axles...? Did the problem run across my car? I went to my discount auto parts place i always go to and my axles go for $70 each + $50 each that i get back when i bring them my old axles. How much is labor for this type of job? Do I really need both axles or is he trying to get me for my money? (Im going to get a second opinion, but not anytime soon)