I have a pea size ball under my stmach skin no pain full been there for like a year no grow any more?

Likely cyst: This sounds like it is most likely a cyst which is benign. Other possibilities are other benign skin tumors from the sweat glands and a lipoma. A malignant tumor while possible, at your age it us less likely. However if it bothers you or changes in size it would be best to see a dermatologist or plastic surgeon to have it removed to make sure what it is.

Hard to tell: without an exam, It may be a lipoma or cyst. Those are the two most likely answers, but needs an exam to be able to answer your question.