It could be a "Morton's Neuroma." Have you seen a doctor to get a diagnosis?
Despite the name, MN is not a true tumor, and Morton was not the first to classify it (a chiropodist named Durlacher was). The condition was misnamed and misclassified a long time ago, and the name stuck, although many in this medical field have fought to have the condition renamed and reclassified to interdigital perineural fibroma or peripheral nerve entrapment, etc. MN is the scarring of the nerve sheath caused by compression/entrapment.
The #1 cause of MN is the types of shoes we wear, shoes that have a narrow toebox and/or elevated heels. Narrow shoes pinch and compress the nerves between the metatarsal bones, and elevated heels force our weight to be carried over the balls of our feet leading to more compression of the nerves. This is why women are more affected by this condition than men, but men do get it too.
If we would have stayed barefoot from birth we would never experience MN. Third world countries don't have this ailment or most of the foot conditions we have in so-called "developed" countries.
Regardless, if you are in the beginnings stages of a developing MN, there's a chance you can calm it down before it becomes full blown, but it COMPLETELY depends on the choices you make from here on out.
Rest it as much as possible. Don't wear shoes unless you have to. When you do, only wear shoes with wide toeboxes and no elevation (zero drop). Consider a metatarsal lift/pad placed properly in your shoes for when you do have to wear shoes. Ice it every chance you can, if you can. (Ice always bothered mine but helped others.) Don't run AT ALL. Don't walk long distances. Avoid surfaces that bother it, barefoot or shod (soft surfaces always bothered me when barefoot, such as, carpet, sand, and grass).
If you show improvement after a few weeks (yes, weeks) of doing this then that means you may have reduced the the inflammation and calmed down the nerve (although it can reoccur again later) and that your nerve has not yet "scarred." Once the nerve scars, then you have developed a full-blown MN, and other more invasive treatments will have to be considered. We can talk about those when the time comes.
In the meantime, just know that if your doctor recommends cortisone shots, alcohol sclerosing injections, or alcohol neurolytic injections (there's a big difference between the later two) you will develop scar tissue, as any injection of any kind will cause scarring of the surrounding tissues. Scar tissue upon scar tissue will make your condition worse. We can talk about that too when the time comes if you'd like, but first please try to calm it down on your own.
Remember that when you feel that nerve firing, it means you have done something or are doing something to aggravate it, and therefore you are adding more scar tissue to it.