if your doctor prescribed them then I wouldn't be too worried obviously your doctor felt it was safe to give them to you. And yes, you should have had a reaction by now if allergic. Why would you think you are allergic?
If it's a drug that the OP has never taken before the doctor would have no way of knowing whether or not they were allergic or it was "safe". As I said above, people who are allergic don't get an allergic reaction the first time they take it. I am mild-moderately allergic to codeine but it didn't give me a noticeable allergic reaction the first time I took it. Taking it once with no problems does not mean anything.