The prominent inner edges of ribs 7 and 8 near the sternum can be shaved down. What you have to consider is that there will be a small scaroin each side to do so. Total surgical costs would be in the range of $5500.
Yes, the rib cartilage can definitely be modified, but to have any detailed ideas about what would work best for you would require an examination, so set up a couple of consults with board certified plastic surgeons and see what they say.
You are thin so this becomes more noticeable. The most prominent areas of ribs 6, 7 and 8 can reduced. There would be a 2 inch scar on each side. You would need a general anesthetic so total cost would be in the range of $4900-5400. Make sure you see a an experienced surgeon board certified by the American Board of Plastic Surgery.
Your ribcage protrusion is quite common. I would be hesitant to undergo any procedure to shave or reshape your ribcage. In addition to the scarring, you can have significant pain from the procedure or numbness from damage to the intercostal nerves that run right under the ribs. These bulges tend to become less prominent as you age.
You look great and there is nothing wrong. You are thin which makes your ribs more prominent. Enjoy it. As you get older, if you gain weight it will be less noticeable.