Knot near the sternum

I was diagnosed with costrochondritis about 3 years ago and shortly thereafter I developed a "knot" in my chest near my sternum. I only occassionally have a dull pain in that area. Although there is what feels like a rounded portion near my sternum it does feel somewhat linear in that it seems to run across my chest - it just doesn't protrude as much as the "knot". And, the knot doesn't protrude so much that you can see it through my skin, just when I run my hand down my chest. Any ideas?