Tietze's is basically costochondritis (rib pain). The probability of malingering depends on what they have to gain from this pain. It is caused by repeated minor trauma to the ribs from coughing or impact, etc. It should usually be pretty short lived but it is not uncommon for someone to focus on the pain and get into this cycle: "I wonder if it still hurts there?" -> *rubs spot, causing pain/inflammation to re-flare* -> "Yep, it still hurts. This pain will never go away!" Repeat in 1 hour. Stress and depression encourage focusing on physical pain that a normal person would be able to ignore. By diverting them away from thinking about the pain and encouraging them to STOP TOUCHING it all the time you can usually help them be pain free. Or maybe this person has chronic bronchitis or plays football a lot and keeps reinjuring themselves from these?
One more thing: It is important that they know that this is not dangerous. Sometimes that reassurance is what patients want . . . but sometimes not.