yes it's fine up to the point where it gets uncomfortable for you. When you get bigger you won't want to sleep on your front but at this early stage, any sleeping position you like is totally fine. Your baby is very well protected in your pelvis and you won't squash it.
Once you get into the 2nd trimester and you get a bump, you may want to start trying to use pillows etc to train yourself into sleeping on your left hand side. This is supposed to be the best position for later pregnancy as when the bump gets really big, lying flat on your back for a period of time may cut off circulation to the arteries that are being squashed by your bump.