A subungual exostosis is a bony growth that may occur under the toenail, and is often times the result of trauma or injury to the toe that results in the formation of the bony irregularity. When the growth causes pain or discomfort, removal of the spur is the treatment of choice. Other small tumors called osteochondromas and enchondroma can also form in the bone beneath the toenail as well as in other bones in the body.