Vicodin is actually ok to take during pregnancy if you are prescribed them for pain and take the smallest dose. I was in a car accident during the first trimester of my last pregnancy and was prescribed vicodin. Doctor said as long as I took it in moderation and only when needed that it shouldn't do any harm. But like with everything during pregnancy, the best thing to do would be to contact your doctor and see what they think and maybe get an ultrasound to reassure yourself.
The only person who can advise you on this is your OBGYN. You definitely need to get in to see an OBGYN ASAP to have an ultrasound done to see if anything is wrong. Only time will tell if damage has been done to the baby or not. Plenty of women take medications and drink (etc) and have no problems and there are others that do it once or twice and have problems with their babies. It is really a toss up, but since you didn't know there is really nothing you could do and it was not like you were using them illegally because you were prescribed them. Just take care of yourself and see the doc and have prenatal testing done and hopefully things will turn out well for you and your little one.