Just a thought. Last year I had a sharp pain in my other big toe. As the day went on it got worse and worse so I decided to investigate. I saw a tiny black thing just under the toenail so got the tweezers out. To my surprise I pulled out a HAIR just over an inch long It was one of my dog's hairs After I removed the hair I didn't have any more problems. Seemingly, hairs getting under toenails is quite common among hairdressers. Just a thought because they can be difficult to spot.