Thanks for your question on Health Care Magic.
I can understand your concern.
Costochondritis is inflammation of of cartilagious joints of
rib cage.
This condition heals by its own slowly, but you need to follow these steps strictly.
1. Avoid movements causing pain.
2. Avoid heavyweight lifting and strenuous exercise.
3. Avoid bad postures in sleep.
4. Start painkiller and anti inflammatory drugs.
5. Apply warm water pad on affected areas.
6. Wear rib belt to prevent mobilisation of painful areas.
No specific diet is needed for this. You need proper rest and above mentioned treatment for recovery.
Hope I have solved your query.
I will be happy to help you further.
Wish you good health. Thanks.