That is an excellent question and one that should be best answered by your primary care doctor
as he or she will be able to perform a detailed history and physical exam to determine the cause of this strange pain and feelings that you are experiencing. In short, there are several possibilities for what this could be but due to the minimal history given, it is difficult to be certain. Do you have any history of diabetes? This can sometimes cause people to have complaints of severe pain in their feet, due to damage to the nerve fibers (aka diabetic neuropathy). There are medications that can help with this if this is indeed the cause. Another potential cause is that you may have gotten a splinter or other damage to your foot which has lead to a small underlying infection which could give you the sensations that you are having. Another possibility is that you have plantar fasciitis, or stress fractures that may be giving you these sensations. Again, the best option is that you are evaluated by your primary care doctor or podiatrist to best evaluate and treat you in an appropriate manner.