Hopefully, it turns out to be nothing. Did you have intercourse recently? That can cause spotting.
I had pink/brown spotting off & on throughout my first trimester to about 13 weeks. It was mostly when I wiped (sometimes a couple drops on a pantyliner), but just a tiny amount. It always went away after a day and then would come back a week or 2 later. I'm 25 weeks now and so far, everything is fine.
One of the times I spotted also corresponded with a yeast infection coming on, and I know sometimes pregnant women will have a bit of spotting if they develop a UTI as well. I don't know exactly what caused my interminent spotting, but I wanted to reassure you that you can spot a little in the first trimester and still have everything turn out OK.