Yes, a guy is still going to like you, regardless of what your boobs look like.
A C-cup isn't a huge difference and in all honesty, it's natural for one breast to be large than the other, due to the muscle development on the dominant side.
You could possibly try doing certain exercises that work your pec muscles, which would help lift and even out the different in your boobs more, but in all honesty if I were you I wouldn't even worry. You'll probably find that while you're paying attention to it constantly, other people can't really tell or notice a difference.
I went through my teens feeling freakish. Then, I realized I was the only one who really paid much attention to them other people really couldn't tell. I had my share of boyfriends and they were all ok with it. (One used to say it was like having the "best of both worlds" and he didn't think it was weird at all.)
- Quote
Most women haven't had a problem telling their boyfriends (see quote above), from what I've read and stuff, so try not to stress or worry about it. 
"Respect yourself enough to walk away from anything
that no longer serves you, grows you or makes you happy."
