Hip Pain - Thoughts?

I have had some inner hip pain around my joint after my 4 mile (each way) commute the last few days. It's a pretty new bike but I did have it professionally fit.

I suspect that it could be that I have a solitary pannier on the side I am experiencing the pain on, but from what I know saddle adjustment (I have had the saddle adjustment checked, but not specifically for hip pain) or even the gearing (it's a single speed, but my commute it relatively flat and I never need to push myself) could be factors.

Any thoughts? I am going to run by my LBS this weekend and tell the fitter about my pain and see what he says, but I would like to know if anyone has been through this before or has any other insight. Thanks!