This issue is fairly common, as stated in the link in post # 4, and has been addressed numerous times here. It is common in the skiing world where people can spend upwards of $1000 on ski boots. In the ski world, boot fitting is a specialized skill requiring special training. I've had this problem myself, both with ski boots and cycling shoes. While there can be several causes, the most common cause is ill fitting footwear and incorrect foot bed for the sport in question.

Assuming your problem is due to the most common cause, here is what a boot fitter describes as the cause. The foot is designed similar to the hand with a small hollow in the palm. When the foot is working hard in too tight of a boot, it is squeezed into a narrow shape that causes numbness or a hot spot. In many cases, the current boots will be fine with the addition of a correct foot bed and or adding a metatarsal bed to an existing foot bed. In my case, simply adding a metatarsal pad did the trick, both in my ski boots and bikeing shoes. This pad does the same job as arch support does for some people.

While resolving the problem, rolling a tennis ball under your foot helps ease discomfort in the same way that hard massage eases knotted muscles.