What Is The Growth On The Second Toe Of The Foot?

my daughter is 12 and has a growth on her second toe on her right foot. It is under the skin and not on the skin itself, like a cyst, right at the mid part of the toe. She weighs about 100 lbs and is very active ... a cheerleader and does gymnastics. It is tender when touched and she does have some constant dull ache with it. No other significant medical history of anything. Very healthy kid.