It's normal to hear a voice in your head, thoughts, ideas etc. I sometimes hear other stuff as well and thoughts i don't think are my own but people seem more concerned about the ones outside your head so i stopped telling. There is "thought insertion" but that is usually with schizophrenia which is serious so i think people would notice if you had that. Try not to worry or focus on it to much try, if doesn't clear up or you are in doubt you could always book a doctors appointment and see what they say.
Was it first time uplifting were hearing them? There are different sources of voices, some people hear theirs in their head, for some it can be a person/people making comments on their actions from outside the head. What's it like for you?
Also, it is quite common to hear voices just before you fall asleep.
We all have an internal narrative...it is the voice of reason (or not) that narrates what is happening, how we are feeling, etc. It is when we confuse that for an external voice that there might be difficulties or when that voice does not serve our best interest...I hope you only have wonderful voices as you deserve nothing less, J
I definitely agree that we all have these narrative like voices and sometimes I'll even argue with myself or debate a decision or something I've done. Its more like examining whats going on and thinking about things verbally in my mind, than doing it out loud.
Don't worry yourself, but if it is something negative or you feel it is something causing you more anguish then I'd suggest going to the doc or the drop in center and having a chat with someone.
Hearing voices in your head is often a sign of schizophrenia, but there are other possibilities as well. It could be that you have a psychic ability to tune into other people's thoughts? Do you remember what the voice was saying?