I agree with Relatively Prime that you should be concerned and whatever you do, don't tell an interviewer that you got a poor grade because you found the class boring because many aspects of medicine are tedious and somewhat boring. An entry level botany class should be fairly simple so there is really little excuse for a poor grade, if you don't care for botany then take something else. Having said that, a "C" in a lab probably won't hurt you that much (GPA wise) unless it is a 3 hour course. The thing that you have to realize is that it is very easy to fall into the "ok, I got a C here but I'll just get all A's from here on out and I'll be fine" frame of mind. Classes get exponentially harder as you progress and you may find it extremely hard to get an A. I have no idea what your major is but every major has classes that are real bears. I was a biochem/micro/molecular major and physical chem for chem majors was required for a whole year and there were no "A's" in our class one semester. The class averages on the exams ranged from in the 40-65% range. I managed to pull a B+ but only because I consistently had the highest grade. The bottom line is that what's done is done and you can't change it but do not use up your lower grades on simple courses because you WILL most likely need them later on when you get to the difficult stuff.
I ended up with one "C" the year that my Grandfather was dying of cancer and a couple of B's and my GPA still ended up at 3.8 so it is not that big of a deal. When the interviewers ask about the "C", I told them the truth, that we were taking care of my grandfather at home who was dying and I wasn't getting any sleep, I was missing too many classes, and school was not my first priority that semester. I made no apologies for it. They were fine with that. I also told them that now in hindsight, I should have taken a LOA that semester but at the time, I too stupid and proud to admit that I couldn't do it all without something suffering.
They actually commented that my honesty was refreshing and they like it when students admit mistakes rather than come up with excuses.