Hi Muskoka and welcome to Project Meditation,
Sorry I missed your post earlier when you posted, I do usually try to ensure I read all the new posts and reply where necessary.
To answer your question...
When meditating, we can experience all sorts of things, whether that's just thoughts, or colours and shapes in our vision, or emotional, mental or physical sensations. The best thing to do is to just accept that this happens (unless you're really in some sort of pain or discomfort) and bring your focus back to your meditation practice and let the sensation pass. Of course, if you are uncomfortable whilst meditating, it is not wrong to just sort yourself out and make yourself comfortable and then continue with the meditation practice.
The sensation you describe could relate to various things, and that could also depend on your beliefs or understanding of things. I could say that it sounds like a movement of energy around your conception vessel meridian (
The Governing Vessel) or perhaps you are increasing the store of Qi (Chi/Ki) energy in your body through your practice. It is certainly likely that it is energy related sensations, but how you wish to interpret that is up to you and whether you are interested in meridian energy principles (the same principles use in accupuncture, EFT etc.)
One thing you can be sure of, there's nothing wrong in what you have experienced.
Hugs
Giles