This does sound like it is closer to the valve at the end of the esophagus between the stomach. This is the valve that is involved when there is acid reflux.
It is possible something is stuck there. Sometimes if you take any medications, a pill will get stuck and then as it dissoves, irritate the mucosa or even make an ulcer. Or a rough piece of food or a piece of meat that had bone in it that you did not realize irritating the area is another possibility
It is also said that stress can cause this area to tighten. Only you can say if you think you have had more stress lately and somehow if this is the part of your body that is showing the effects. (if you do feel you are under a lot of stress, I have a good reference for you, if you like).
If this continues, you will may need to have an EGD to find out what the problem is. An x-ray might be done first.
I found some information from an ENT's web page regarding this conditions that also mentions possible canker sore or a type of diverticulum. See:
Let me know if you have any other questions about this that I can help you with. Oh, you may want to try some liquid maalox and see if it helps, just in case there is some irritation there. Sometimes there is no burning even when some gastric juice may have irritated the area, especially if this is the first time it has happened - it may not burn yet because the tissue has not been deeply effected yet.