Stiff Neck. A cause of concern for me?

I had a stiff neck towards the end of January after a trekking trip. I thought it might be due to carrying too much weight and sleeping in a position that stained my neck. The discomfort stopped after 4-5 days so I didn't pay much attention to it. But, since then I've actually been having this problem quite frequently. However, the subsequent episodes haven't been as extreme. The range of motion of my neck is pretty good. The discomfort only arises when I move my head to the extremes. I never had any neck or shoulder pain issues prior to the incident. But it seems to me that now my neck has becomes a lot more tender. As an example, it'd get a bit stiff if I sleep on my stomach for even 15-20 minutes. I must add that I've been traveling quite a bit since the end of January and have a feeling that long journeys coupled with me having to sleep on different mattresses and pillows is aggravating the pain. Should this be a cause of concern for me?