According to WebMD and ZocDoc, tingling in the bottom of the feet might indicate nerve damage, high levels of blood sugar, nutritional deficiencies, low amounts of thyroid hormone, syphilis or Lyme disease. However, it can also be completely benign and temporary.
If the tingling is in the form of a pins and needles feeling and is painless, it is likely to be the result of physical pressure on the nerves, as in the case of crossed legs. WebMD suggest seeking medical evaluation if the tingling persists. Over time, persistent tingling can lead to more serious issues such as decreased mobility or disability.